PROCEEDINGS

OF THE

PHOSPHOGYPSUM FACT-FINDING FORUM

Co-sponsored by

FLORIDA INSTITUTE OF PHOSPHATE RESEARCH1855 West Main Street

Bartow, FL

and

THE FLORIDA CENTER FOR PUBLIC MANAGEMENTFlorida State University

Tallahassee, FL

and held at

August B. Turnbull, IIIFlorida State Conference Center

Tallahassee, FL

December 7, 1995

February 1996

DISCLAIMER

The papers in this report are reproduced herein as received from thespeakers. Transcripts of the question/answer sessions were made from theactual videotape of the Forum.

The opinions, findings and conclusions expressed herein are notnecessarily those of the Florida Institute of Phosphate Research, nor doesmention of company names or products constitute endorsement by theFlorida Institute of Phosphate Research.

PHOSPHOGYPSUM FACT-FINDING FORUM

EXECUTIVE SUMMARY

The Florida Institute of Phosphate Research and The Florida Center for PublicManagement at Florida State University co-sponsored this Fact-Finding Forum on December7, 1995 in Tallahassee, Florida. The purpose of the Forum was to expose the audience and aselect panel of Florida state and local government decision makers to a scientific discussion ofthe effects and uses of phosphogypsum.

In assembling the best national and international scientific talent for presentations, theFlorida Institute of Phosphate Research staff made a determined effort to include scientistswith opposing views on the effects of using phosphogypsum. However, it was very difficultto find scientifically-trained speakers, or groups who could recommend such experts, on thenegative impacts of phosphogypsum usage. This factor understandably gave the panel andaudience the perception that the presentations were unbalanced. We very much regret that,but it should not detract from the quality and value of the information presented at the Forum.

CONCLUSIONS FROM THE FORUM PAPERS AND Q & A SESSIONS

Environmental Effects of Phosphogypsum (PG)

1. There is no significant risk to human health for those individuals working with oraround PG; for example, those building a road or spreading it agriculturally.

2. Whereas shielding materials placed over PG are able to protect people rathercompletely from the impacts of radon, they are less effective in attenuating gammaradiation, so that the gamma factor must always be considered.

3. There appears to be no significant risk to someone traveling over a phosphogypsum-based road, but only to someone who might build a house on it and occupy that housefor 70 years (EPA scenario).

4. The marine studies at Louisiana State University employing PG/cement structures asoyster clutch substrates or artificial reefs have shown no bioaccumulation of toxicmaterials to date, but these studies need to be extended over longer periods to giveconfidence in the results.

5. The use of PG as a cover material in municipal waste landfills accelerates thedecomposition of a “standard garbage” and has the promise of providing additionallandfill space, but it also increases the evolution of hydrogen sulfide. There istechnology available to recover economically the sulfur values of the hydrogen sulfide.

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Uses of Phosphogypsum

1. Much structural and environmental data have been accumulated by various researchersin the use of PG in county and secondary roads, but its use in federal and state heavy-duty roads needs additional research.

2. Compelling economic benefits have been calculated for constructing county roadsusing PG mixtures.

3. Realistic agricultural PG application rates of from 250 to 500 lbs/acre/year constitutesan acceptable risk, even using the USEPA’s conservative limits.

4. Preliminary economics show a distinct cost advantage to farmers or cattle ranchers inusing PG to supply soil calcium or sulfur, and in improving the soil structure.

5. The economics of using PG in marine structures, as well as the environmental risksinvolved, need confirmation before this proposed use can be taken seriously.

Miscellaneous Interesting Points Made by the Speakers

1. The Canadian level of concern (action level) on radon is more liberal than USEPA’s(roughly 5 times our 4 pCi limit).

2. The USEPA has set very low limits on acceptable radiation levels - of the order of 70mrem/year - very close to the average USA background level.

3. Although the USEPA has stated that they are going to relax the present limit of 700Ibs of PG they allow to be used for research purposes, it is probable that anydemonstration-scale experiment will still require a variance.

The policy panel and the audience showed great interest in the uses and the effects ofusing PG. Discussion was often lively about what could be done to liberalize present USEPArules so as to allow larger, demonstration-type projects using PG.

The panel proposed that FIPR and USEPA adopt a cooperative approach to resolvingdifferences about the effects, uses and policies governing PG.

Dr. Larry K. GrossDirector, Florida Center for Public ManagementFlorida State University

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HEARING PANEL POST-FORUM POSITIONON PHOSPHOGYPSUM

The Florida Institute of Phosphate Research has concluded from its experimentalstudies on phosphogypsum (PG) and those of other researchers that much of theofficial concern about the perceived environmental and public health risks of PG isreasonably debatable. Many of the proposed uses of PG appear to involve levels ofrisk which are below regulatory concern or which can be mitigated using currentlyavailable practices. Therefore, in light of the potential economic advantages of theproposed uses of PG, and the demonstrated environmental and economic penalties ofstacking and monitoring PG, the Institute is seeking a partnership with the USEPA toset acceptable standards for current PG use and large scale research and demonstrationprojects.

Further, on completion of such large scale research and demonstration projects andsubstantial, appropriate peer review, USEPA policy should be reviewed to reflect thescientific consensus of the risk and of demonstrated mitigation measures governing theuses of PG.

1/29/96

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PHOSPHOGYPSUM FACT-FINDING FORUM

DATE: Thursday, December 7, 1995

TIME: 8:30 a.m. - 5:00 p.m.

PLACE: August B. Turnbull, IIIFlorida State Conference Center555 West Pensacola Street(Four blocks west of the Capitolcomplex)Tallahassee, Florida

RECEPTION: 5:30 p.m. - 7:00 p.m.22nd Floor, the Capitol

The Florida Institute of Phosphate Research Board of Directors is sponsoring a fact-finding forum concerning phosphogypsum - its potential risks and its potential benefits.

Board members are conducting the forum as part, of the Institute’s pro-activephosphogypsum program, which is striving to find the best way to deal with thecontroversial phosphate processing by-product that now sits in 27 stacks, 10 of whichare active. Hundreds of millions of tons of phosphogypsum have been created inphosphate processing and approximately 30 million new tons are created each year.

The Environmental Protection Agency has passed regulations that prevent the gypsumfrom being used because of its trace amount of radium. Research the Institute has fundedindicates that the EPA’s risk analysis may be overly cautious and that the economicbenefits of putting gypsum to use in agriculture, road building, construction and otherproven areas could save money for taxpayers, farmers and the state.

The December forum is intended to air the facts before regulators, lawmakers,environmentalists and others in hopes of launching further discussion about putting thiswaste product to use and solidifying a FIPR position on the issue.

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PHOSPHOGYPSUM FACT-FINDING FORUMINTRODUCTORY REMARKS

BY

M. JACK OHANIANCHAIRMAN, FIPR BOARD OF DIRECTORS

* * * * * * * *

Author: M. Jack Ohanian - Associate Dean for Research & Administration, College of Engineering,University of Florida

Dr. Ohanian, immediate past chairman of the American Association of Engineering Societies (AAES) and pastpresident of the American Nuclear Society, has recently been appointed by the Governor of Florida to hissecond term on the five-member Board of the Florida Institute of Phosphate Research. He serves as Chairman.Dr. Ohanian’s research interests and his (over 60) technical publications have dealt with nuclear reactordynamics and safety. More recently he has focused on nuclear energy systems, their safety and public energypolicy. He serves on the Review Committee for the Reactor Engineering Division of Argonne NationalLaboratory and the Safety Oversight Committee of Florida Power Corporation’s Crystal River Nuclear Plant.

Dr. Ohanian received his bachelor’s degree in electrical engineering from Robert College (Istanbul, Turkey),and a master’s degree in EE and a Ph.D. in Nuclear Science & Engineering from Rensselaer PolytechnicInstitute.

* * * * * * * *

Good morning Ladies and Gentlemen! I welcome you on behalf of the Board of Directors of the FloridaInstitute of Phosphate Research. We appreciate the fact that you have taken the time and effort to attend a forumconcerning an industrial by-product, phosphogypsum (PG), about which the average Florida citizen is notwell-informed or may even be misinformed. Many of those who have heard about PG have heard statementsabout its impact on public health and the environment. Today, we will present to our “Policy Panel” a numberof speakers, each one an expert in one or more aspects of PG: its possible uses, the economic attractiveness ofusing it, and the environmental/public health risks involved in its use.

Chemically, PG is calcium sulfate dihydrate or gypsum, produced by the reaction of phosphate rock withsulfuric acid during the process of producing phosphoric acid, the major ingredient of vital phosphate fertilizers.Gypsum is a very common inorganic compound with a myriad of industrial uses. The term “phosphogypsum” isused to specify the particular gypsum arising from the acidulation of phosphate rock, because it contains traceamounts of many of the mineral impurities that accompany phosphate rock. Of these impurities, perhaps themost notorious is radium, the parent of radon. Other trace impurities found in PG include fluoride, chromium,lead, zinc and uranium. But, it is primarily the radon concern that led the United States EnvironmentalProtection Agency to restrict uses of PG and to stipulate that no PG with radium over 10 pci/gm can beremoved from the PG stacks adjacent to the chemical plants.

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This limit was intended to insure that the risks from indoor radon and direct gamma radiation exposure inresidences constructed on land previously treated with PG do not exceed an acceptable level.

It is this EPA restriction, promulgated on December 15, 1989, and issued after several legal challenges on June3, 1992 (Federal Register Vol. 57, No. 107 - 40CFR Part 61), that has frustrated the many proposed uses of thePG by-product in non-residential uses. Hundreds of millions of tons of PG have accumulated in Florida aloneover the last 50 years. The industry has researched many proposed uses for PG in an effort to do what the EPAencourages with other industrial by-products . . . .recycle. Before the EPA restriction, a limited number ofeconomic uses for PG had been developed for agriculture, industrial plant access roads and parking lotconstruction; now these uses are precluded.

At the outset, I would like to stress that when this forum was conceived, we intended to have several EPAspeakers on the program. However, when we issued them an invitation and strongly encouraged theirparticipation, we were informed by EPA Washington that their attorneys would not allow them to attend becauseof the legal challenges I mentioned. They did ask that we send them a copy of these proceedings and invited usto meet with them and “continue to work toward resolving some of the environmental issues associated withphosphogypsum”. We certainly intend to do that!

While there is controversy over the effects of low levels of radon on human health and the validity of thecurrent EPA standard for indoor radon, this will not be the focus of this forum. Rather, we will present to thepolicy-makers testimony that there are economic advantages to using PG that benefit the public and the industry,and that such uses involve little risk to the public or to the environment.

As our program indicates, the first session will highlight agricultural uses, the second will feature miscellaneoususes of PG, and the afternoon speakers will discuss the potential for construction uses of PG. Following thethird session, we will ask the various risk experts to comment on what they have heard and close withcomments and observations from our panel members who have listened to and questioned the various speakers.

At the conclusion of the formal program, I invite all of you to a reception, starting at 5:30 on the 22nd Floor ofthe Capitol Building.

In summary, in keeping with the Institute’s legislative mandate to take a leadership role in assessing andresolving phosphate issues that affect the environment and the health and safety of Florida’s citizens, we presentthe following thesis to the assembled Policy Panel. We will ask them at the end of the day to agree with,modify, or disagree with the following FIPR position:

“FIPR has concluded from its experimental studies of phosphogypsum and its characteristics that much of theofficial concern about PG’s perceived environmental and public health risks is misplaced. Most of the proposeduses of PG involve minimal risk, and that minimal risk can be readily mitigated using common sense and well--established practices. Therefore, in light of the economic advantages of several of the proposed uses ofphosphogypsum, the US EPA should be strongly urged to reevaluate its restrictions on the utilization of PG”.

Before we begin today’s presentations, I would like to introduce to you my fellow members of the FIPR Boardand the other Policy Panelists who have generously given of their time to help us arrive at a conclusion at theend of the day.

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THE REGULATION OF PHOSPHOGYPSUMCHAPTER 62-673, F.A.C.

PHIL CORAM, P.E.DEPARTMENT OF ENVIRONMENTAL PROTECTION

* * * * * * * *

Author: Phillip Coram, Florida Department of Environmental Protection.

Mr. Coram has been the Administrator of the DEP’s Industrial Wastewater Program for the last six years. Heis responsible for rule and policy development and has served as a member of the technical Workgroup for thePhosphogypsum Management Rule. He was a member of the EPA’s Dialogue Committee on phosphoric acidwastes, and is currently a member of the FIPR Policy Advisory Committee. During his 14 years with the DEPhe has worked with a variety of programs including drinking water, air, solid waste, hazardous waste,stormwater and domestic wastewater.

Mr. Coram is a graduate of the University of Florida with a degree in environmental engineering, and is aRegistered Professional Engineer.

********

Background

Florida has over 20 phosphogypsum stack systems located at phosphoric acid fertilizer manufacturing facilitiesin Polk, Hillsborough, Manatee and Hamilton counties. Ground water monitoring at these stacks, begun in1986, has shown that a majority of the stacks, at some time, have caused exceedances of drinking waterstandards (primarily sodium and sulfate) at the facilities’ property boundaries in the surficial aquifer, or havecaused increases above background concentration and/or exceedances of standards in the intermediate orFloridan Aquifers.

It was apparent from the ground water monitoring that phosphogypsum stack systems were facilities reasonablyexpected to be a source of pollution within the meaning of section 403.087, Florida Statutes, and that specificstandards were needed for stack construction, operation and closure. Rulemaking on phosphogypsum stacksystems was, therefore, initiated by a November 29, 1989 Policy Memorandum issued by former Department ofEnvironmental Regulation Secretary Twachtmann. The policy memo established interim criteria for permittingand enforcement, and directed the Division of Waste Management, in coordination with the Southwest Districtand Division of Water Facilities to initiate rulemaking on phosphogypsum disposal.

Rulemaking

Rulemaking initiated shortly thereafter, with three workshops held in 1990-1991 in Jacksonville, Tampa andTallahassee. The two major groups involved in the rulemaking were the Florida Phosphate Council, an industrytrade association, and Manasota-88, an environmental interest group. There were two main issues debatedduring the workshops: 1) liner design reguirements for stacks systems, and 2) closure dates for existing unlinedstack systems. Manasota-88 argued for stringent RCRA hazardous waste type liner requirements and for closureof existing unlined stack systems as soon as possible, while the Council argued for less stringent linerrequirements and the ability to continue to operate the existing stack systems.

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Much of 1992 was devoted to evaluating various liner design standards. Ardaman & Associates, consultants forthe Council, prepared a series of technical reports on a proposed liner design which utilized compacted gypsumas the upper component of a gypsum/synthetic membrane composite liner. This design was peer reviewed bynationally recognized experts on liner systems, and was found to have a low leakage rate that modelingindicated would not cause violations of ground water quality standards.

In January 1993, Chapter 62-673, Florida Administrative Code, Phosphogypsum Management ( the “Rule”),was adopted by the Environmental Regulation Commission (ERC). The major elements of the Rule include:

62-673.200, DefinitionsSeventeen terms are defined, including: phosphogypsum, phosphogypsum stack, phosphogypsum stack system,process wastewater, closure, final cover, lateral expansion and liner.

62-673.220, ApplicabilityProvisions relating to liner and leachate collection are intended to apply to all new stack systems and lateralexpansions of existing stack systems.

62-673.300, ProhibitionsPhosphogypsum is prohibited from being disposed outside a permitted phosphogypsum stack system. However,this prohibition does not preclude the use or reuse of phosphogypsum if otherwise allowed by law. Radioactivematerials can only be disposed according to the requirements of the Department of Health and RehabilitativeServices.

62-673.310, Alternative Procedures and RequirementsThe use of procedures other than those specified in the Rule are allowed if they provide a level of protection tohuman health and the environment equal to that required by the Rule.

62-673.320, Permitting of Phosphogypsum Stack SystemsDescribes the process for permit application and processing. Prescribes application information requirements.

62-673.340, Phosphogypsum Stack System General CriteriaSpecifies performance criteria and location requirements for stack systems.

62-673.400, Phosphogypsm Stack System Construction RequirementsDescribes construction reguirements for liners, leachate control systems and other components of the stacksystem.

62-673.500, Operation RequirementsDescribes operational requirements, including ground water monitoring, surface water management and leachatemanagement.

62-673.600, Closure of Phosphogypsm Stack SystemsDescribes the process by which stacks are to be closed, including provisions for temporary deactivation of astack because of economic conditions, the development of a closure plan, and the requirements for final cover.

62673.610, Closure Plan RequirementsDescribes the required components of a closure plan, including the final cover for the stack system.

62-673.620, Closure ProceduresDescribes the procedure by which a stack system is finally closed.

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62-673.630, Long term CareRequires the monitoring and maintenance of a stack system for 50 years after closure, methods for maintainingleachate and stormwater control, and long-term ground water monitoring. Provisions are included for a reducedlong-term care period under certain circumstances.

62-673.640, Financial ResponsibilityDescribes the process for estimating the costs of closure and long-term care, requires that a bond be postedequal to the costs of closure, and makes provisions for alternative financial instruments such as a letter of credit,trust fund agreement, closure insurance, financial test, and corporate guarantee.

62-673.900, FormsProvides the forms to be used for permit application to construct, operate, and close a stack system, certificationof construction completion, and for financial instruments.

The issue of closure of existing unlined stack systems was left open at the January ERC rule adoption hearing.The Department had proposed rule language requiring all existing systems which cause ground watercontamination to stop accepting phosphogypsum within eight years and to complete closure in an additional fouryears (referred to as the “date certain for closure”). The industry argued that premature closure of these systemswould be a tremendous economic burden. The Department’s proposed language and a joint Department andIndustry compromise amendment predicated on a legislative proposal were not adopted by the ERC. TheCommission directed the Department to revisit the closure issue after the legislative session.

New Legislation

The Department and the industry in the 1993 legislative session successfully resolved the issue of existing stacksystems by establishing the phosphogypsum management program, section 403.4154, Florida Statutes. The lawauthorizes the Department to assess registration fees on phosphogypsum stacks, and provides the Departmentwith staff and resources (8 positions, $500,000/yr.) to:

1.

2.3.

Review and process requests from owners and operators of phosphogypsum stack systems for relieffrom the mandatory closure provisions.Review and process applications for new or expanded phosphogypsum stack systems.Review and process applications to close systems.

With additional resources, the Department would be able to conduct intensive, site-specific evaluations ofexisting stack systems to determine the adequacy of ground water assessment and corrective action plans toensure compliance with ground water standards. However, the statutory provision for registration fees wouldonly take effect if the ERC adopted rules that provide relief from mandatory closure requirements for existingunlined systems. At the June 1993 meeting of the ERC, the needed rule revisions were adopted.

Closure of Unlined Systems

Section 62-673.650 of the Rule prohibits the disposal of phosphogypsum and process wastewater in unlinedstack systems after March 25, 2001. The systems may be used for water management purposes after this date,but final closure must be completed not later than five years after a system ceases to accept phosphogypsum.Relief from the mandatory closure provisions is provided if an owner of the phosphogypsum stack system candemonstrate:

a) Such system was not causing violations of water quality standards prior to March 25, 1993, and is notexpected to cause violations after that date; or

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b) The owner implements corrective measures to remediate any existing contamination, and such measureswill result in compliance with all water quality standards by March 25, 2001.

Implementation of Rule and Legislation

Since adoption of the Rule and Legislation in 1993, the Department has worked aggressively in implementingthe new rule requirements and legislation. The Phosphogypsum Management Section was created and iscurrently housed in the Southwest District. It is staffed with some of the Department’s most experiencedengineers and scientists. The section was recently presented an Outstanding Achievement Award for its actionsrelated to the IMC-Agrico sinkhole incident.

Permitting of New Stack SystemsSince the Rule became effective in 1993, the Phosphogypsum Management Section has approved a new stackfor the U.S. Agri-Chemicals facility in Ft. Meade, a new cooling pond for CF Industries Plant City PhosphateComplex, and a lateral expansion of a gypsum stack and cooling pond for the IMC-Agrico Nichols facility.

Closure PlansIn September 1993, general plans for closure were submitted for all stack systems regulated under the Rule. Thetotal estimated cost for closure and long-term care of the these stack systems is about $200,000,000. Closureand long-term costs for an individual stack system averaged about $10,000,000.

Financial AssuranceAlmost all the companies have sought to demonstrate financial responsibility for closure of the stack systemsthrough use of a financial test or parent corporation guarantee. However, many companies have found theRule’s financial test requirement that working capital or tangible net worth be at least six times the estimatedclosure and long term care costs difficult to meet.

Because of these financial considerations, the Department contracted with a financial expert to review theexisting financial test requirements as they applied the phosphate industry. Our contractor determined that the6X requirement was inappropriate for the phosphate industry and recommended use of an alternative financialtest to determine the ability of a company to fulfill its closure obligations. Based on this recommendation severalcompanies have been authorized by the Department to use the alternative financial test to demonstrate financialresponsibility.

Summary

The Phosphogypsum Management Rule reflects a practical balance between environmental protection and thecontinued economic viability of the phosphate industry. New phosphogypsum stack systems and existing systemexpansions are being constructed with liner systems that are protective of ground water quality.

Existing unlined stack systems, as highlighted by the IMC-Agrico sinkhole incident, represent a potential forground water pollution. The Department will be closely reviewing the demonstrations required by rule62-673.650 to allow continued use of unlined stack systems beyond March 25, 2001.

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PHOSPHOGYPSUM HANDLING

BY

GERALD J. RUBINIMC-AGRICO COMPANY

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Author: G.J. (Jerry) Rubin, IMC-Agrico Company

Mr. Rubin has been with IMC since 1965 and currently holds the title of Director of Technical Services. Hewas project manager for the New Wales Chemical Plant, including the P,O, section, the feed ingredients plant,the defluorinated phosphate plant, wet rock grinding and uranium recovery facilities. In 1991 he was givenresponsibility for the state-of-the-art phosphogypsum stack expansion, and also oversaw the remediation of thewell-publicized sinkhole in the old stack.

Mr. Rubin is a graduate of Rensselaer Polytechnic Institute with bachelor’s and master’s degrees in chemicalengineering; and is a Registered Professional Engineer in Florida and Louisiana.

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Basic Design and Operation of Phosphogypsum Stacks

For every 1 ton of phosphoric acid produced, expressed as P,O,, approximately 5 tons of by-productphosphogypsum are also generated. In conventional dihydrate plants, such as those predominating in the U.S.,the gypsum is discharged from the phosphoric acid filters, slurried with recycle process water from the plant’scooling pond, and transported to the gypsum stack at 20-25 % solids by weight.

Once there, the slurry is diverted to generally two or more alternate settling areas via pipes or rim ditchesaround the perimeter of the stack. The rim ditches themselves are alternately excavated and used to constructperimeter or cross dams as the stack is raised. As the gypsum particles settle out, the excess transport waterdecants to collection ditches at the base of the stack and ultimately to the process cooling pond, where itco-mingles with recycle process water used in other areas of the plant.

The size of a gypsum stack is generally dictated by the minimum surface area required to settle gypsum andclarify the decant water, the time required for the rim ditch gypsum to consolidate sufficiently for excavation,and the personnel and equipment available for operation/maintenance of the stack. These are in turn generallydictated by the P2O5 production rate of the plant.

For a production rate of l,000,000 tpy of PZ05, and assuming a desired 10 year stack life, approximately50,000,000 tons of gypsum must be stored. For a 200 foot high stack, common in Florida, and based on a final4:1 horizontal:vertical slope, also typical, a land area of approximately 300 acres will be required. Under thisscenario, the top surface area will end up at about 70 acres, which is still adequate for effective settling.

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The IMC-Agrico Gypsum Stack Expansion Project

With the advent of the Phosphogypsum Management Rule in March, 1993, gypsum produced after 2001, whichuntil now had been stored in unlined areas including mined out pits, would now have to be contained in linedsystems. The New Wales Plant of IMC-Agrico Company became the first location in the phosphate industry toconstruct a new phosphogypsum stack on top of a high density polyethylene (HDPE) flexible syntheticmembrane.

The permit application process for the Gypsum Stack Expansion began in 1988 and lasted approximately 2years. Construction began in September of 1990. Because of the size of the expansion area, and to facilitateconstruction and minimize exposure time of the liner, construction was accomplished in two overlapping stagesrepresenting approximately equal areas. The West Area was completed in April, 1992, and the East Area inJune of that same year. Following is a summary of the major segments of the expansion project and the capitalcost associated with each.

Site Preparation $15.8 MM

The location chosen for the Gypsum Stack Expansion Project had been recently mined, and consisted of rows ofspoil piles cast by draglines during mining. A total area of approximately 520 acres had to first be cleared andgrubbed. This was especially important given the fact that a flexible HDPE liner was to ultimately cover thesite. This was followed by excavation and removal of better than l,000,000 cubic yards of soft clays to preventdifferential settlement beneath the liner. Much of the clay was present below standing water of variable depth inthe mine cuts. Dredging and dragline excavation methods were both used.

Earthwork consisted of backfilling the mine cuts, levelling cast spoil piles to pre-set elevations, site grading andconstruction of compacted earthen dikes. Approximately 5,000,000 cubic yards of earth was moved in abalanced cut and fill operation to achieve a uniform liner subgrade.

As previously mentioned, the project was divided in two approximately equal areas separated by an earthendivider dike. A perimeter earthen dike surrounded the entire project site. In order to segregate and controlsurface water runoff, and facilitate and manage construction, each of the West and East Areas was subdividedinto 5 cells separated by earthen divider berms and runoff ditches.

Being that the area was originally a mined out pit, dewatering was a major consideration during both sitepreparation and the following liner installation. Relief trench drains, drainage ditches and large capacitydewatering pumps were all used. All surface runoff, drainage and water from temporary dewatering operationswas contained within the Company’s mined out pits and water circulation systems.

HDPE Liner Installation $16.4 MM

A 60 mil high density polyethylene (HDPE) liner was installed over the entire base of the expansion areaincluding the upstream slope of the perimeter earthen dikes. In order to address the stability of the ultimate 200foot high gypsum disposal area, textured liner was used around the perimeter of the facility, while smooth linerwas installed within the central portion. The overall split was approximately 53/47, textured/smooth. With theexception of the West and East Area Flumes which connected the lined area with the existing cooling pond,there were no penetrations of the liner.

Panel layout and seam orientation was in accordance with the manufacturer’s design. Panel deploymentgenerally proceeded from high to low ground. The center cell in each area was lined last. Wind ballast andanchor trenches were utilized to protect against uplift by wind.

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Adjacent liner sheets were overlapped by at least 3 inches and welded together by one of two different methods.A total of approximately 925,000 lineal feet of field seams was required.

The liner itself was overlain by a system of three concentric drains, comprised of approximately 45,000 linealfeet of slotted HDPE pipe surrounded by silica gravel, and then completely wrapped with polypropylene filterfabric. The drains were constructed atop the liner in drain trenches resting on and covered by gypsum. Eachslotted drain pipe was connected to at least one outlet pipe, which extended along the lined inboard slope of theperimeter earthen dike. The liner on the inboard slope was covered with a 2-foot thick layer of compactedgypsum hauled from the existing stack. An upper and lower discharge was provided to the lined seepagecollection ditch from each outlet pipe. About 11,600 lineal feet of outlet pipes was grouped into approximately18 outlet locations spaced around the periphery of the expansion area.

In addition to the gypsum used for drain trenches and the inboard slope of the perimeter dike, access roads andthe internal gypsum dike were also constructed with gypsum hauled from the existing stack. Any runoff thatcame in contact with the gypsum placed in the lined expansion area during construction, had to be collected anddiverted to the existing cooling pond.

Gypsum was excavated from a borrow area of the existing stack using draglines, backhoes and dozers.Continual dewatering of the borrow area in order to obtain the proper moisture gypsum was a major problem.Approximately 1,200,000 cubic yards of gypsum was “borrowed” from the existing stack, and hauled to theexpansion area via lo-wheel dump trucks over newly constructed roads and bridges.

Concrete Flumes and Other Structures $1.1 MM

As previously mentioned, the only penetrations of the liner were the reinforced concrete flumes directing stackrunoff and seepage to the existing cooling pond for re-use. Each of the two flumes was constructed of concreteand protected by a coal tar epoxy coating. The flumes were approximately 300 feet long, and passed through aperimeter dam, beneath two service roads, beneath two sets of railroad tracks and through a slurry wallseparating the cooling pond from the expansion area.

Another structure that had to be constructed was a box culvert crossing of the existing pond water channelrequired for the trucks hauling gypsum from the existing stack. Other structures included those for gypsumpipelines crossing under railroad tracks and roads.

Gypsum Slurry Pipelines $5.0 MM

Two 30 inch diameter, 9,000 foot long, rubber lined steel pipelines were constructed to transport the gypsumfrom the production facilities to the new expansion area. Over five hundred (500) 40 foot long pipe spools andfittings were required. An elaborate relief system was installed to balance stresses and control pipe movementdue to thermal expansion/contraction.

Engineering/Quality Control $6.1 MM

Ardaman & Associates, by virtue of its acknowledged expertise in the design and construction ofphosphogypsum storage facilities, was chosen to provide all required engineering and consulting services. Itsinvolvement was basically divided into the following four categories:

. Planning and Conceptual Design

. Development of Permit Applications

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. Detailed Engineering

. Quality Assurance and Quality Control

Planning and conceptual design began as early as 1986. Submittal of Permit Applications was targeted for 1988.Due to environmental concerns, they were revised and resubmitted in 1989. A complicating factor was thedevelopment of the Phosphogypsum Management Rule during this same period. As it turned out, the NewWales Lined Gypsum Stack Expansion Project essentially became the basis for much of the Rule.

Engineering required not only the customary basic design, but also justification of numerous technicalinnovations to the Agencies because of the project being a “first”. Key features included:

. Use of a 60 mil HDPE flexible liner, and development of acceptable QA/QC procedures.

. The combination of textured and smooth liner material.

. Development of the unique “composite liner” concept utilizing gypsum atop a synthetic membrane.

. Development of construction sequencing procedures to allow concurrent liner deployment, gypsumplacement, dram construction and runoff management.

During the construction phase of the project, Ardaman’s QA/QC procedures included:

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Determination of clay removal quantities and guidance to the dredge and dragline operators removingsame.

QC inspection and testing during construction of the Relief Drains.

Monitoring of earthwork construction including backfilling of minecuts, rough site grading, perimeterearthen dike construction and fine grading operations.

Density testing of compacted fill.

Review and evaluation of factory testing of liner materials.

Physical testing of delivered liner rolls and sheets.

Non-destructive and destructive testing of field seams.

Monitoring of stack drain materials and placement.

Monitoring of gypsum placement and compaction atop liners.

Monitoring of suitability of gypsum borrow.

During the course of construction, Ardaman provided a resident engineer and a staff of 5 to 20 full-time qualityassurance inspectors, mobilized on an as needed basis.

10

Other Facilities $1.5 MM

In addition to the tasks and facilities associated with the expansion area itself, numerous additional projects wererequired because of the existing gypsum stack. Items such as slurry walls, capping of recharge wells andinstallation of an extensive series of monitoring wells, whose total cost was significant, are not included herein,as they would not be typical for most installations, other than a nominal number of monitoring wells.

Construction Staff/Facilities $1.4 MM

Work on the project began in 1986 with the formation of the Company’s Project Group. Detailed design beganin August, 1990, with field construction beginning in September of that same year. Utilizing “fast track” designand construction, the West Area started up on schedule in April, 1992. A computerized schedule was requiredto track the over 1000 activities associated with the project. Over 50 engineering and construction contractswere awarded, with most being “hard dollar. ” Clay removal and earthwork were “time and material. '’

The Project Group functioned both as owners representative and prime contractor. At peak construction, theProject Team consisted of a Project Manager, a Project Superintendent, two Project Engineers, aCost/Scheduler and three Field Superintendents.

The bottom line capital cost for the Gypsum Stack Expansion Project totaled approximately $49.7MM, notincluding capitalized interest.

11

-From video, transcript of questions and answers of Present Practice Panel discussion:

POLICY PANEL QUESTIONS TO PRESENT PRACTICE SPEAKERS

OHANIAN: Now lets take no more than about 5 minutes and see if the panel has any questions of our twospeakers before we go on to the next panel presentations.

YOUNG: Mr. Coram I think you mentioned that use and reuse under the rule is allowed if not otherwiseprohibited. Could you tell me how that actually translates?

CORAM: Currently EPA prohibits reuse of PG under its NESHAPs regulations so if that regulation waschanged or modified our rule would not prohibit the use or reuse of PG if shown you could do it in anenvironmentally sound manner.

YOUNG: Does that infer that FDEP, assuming that EPA rules were changed to allow it, would not undertakeits own rulemaking or independent review but would defer to the EPA decision? Or would FDEP, at that point,proceed to make its own inquiry and develop its own rules?

CORAM: Well our rule currently classifies PG as a solid waste. However, there are provisions in (chapter)403 Florida Statutes called “Industrial By-Products” where an industry can make a demonstration that thematerial can be beneficially used. As long as it does not represent a threat to human health or the environmentit can be reclassified as an industrial by-product and no longer be considered a solid waste and therefore, wewould simply relinquish reglatory control over that material.

SMITH: For Mr. Rubin, I think in your presentation you talked about putting 24 inches of compacted gypsum,which I am assuming is some of the by-product here. I heard the Chairman say, some of the concern in theregulation that EPA has is based on the radon gases. How are you able to handle those materials, if in fact, theywere a threat to the workers? How are you able to move that gypsum, compact it, if there was a concern forradiation?

RUBIN: I am not sure I know how to answer that question. We do not believe that there is that risk to theworkers.

SMITH: I don’t want to steal Dr. Ho’s thunder. But we have used those materials, and we have measuredthose properties, and we find some of those materials have less radioactivity than the native materials which wetypically use everyday. I was just supporting the comments that Mr. Rubin made, because if you are going dealwith materials that are radioactive, we are all concerned about the fellow worker and you have a lot ofequipment out there and I don’t think you want to contaminate that; but our own use of early experiments withthese materials in 1980, we found no real risk from radiation, our concern was with some acidity of some of thematerials as you bring them in contact with pipes and so forth. This is a real mystery to me, the question onradiation at this point.

COLEMAN: A question that came to me from the audience really fits right in here, and that is how radioactiveis the phosphate gyp. Maybe some one can place a relative risk on it.

13

B. SCHEINER: In the early 80’s we probed every stack in Floridaand did a composite study of radionuclides in all the stacks. The number we came up with was 22 pCi/gramacross the state. You can get the individual stacks out of the data, this has all been published, but that’s whatwe count for the whole state, all 13 stacks at the time, I believe.

COLEMAN: What does that mean, 22 pCi/gram? What are you saying is risk? How do you rate that next toa cigarette?

OHANIAN: Perhaps we should wait on that. We have the risk panel coming up. They will be able to addressthat.

COLEMAN: Fine, then let me go back to another question that was also put forward. Can an additionalprocessing step, such as centrifugal separation, be used to reduce the radiation levels in PG as it is now? Thatmay need to be asked of another group, too. Chemical processing, for example, may want to answer that.

GARRITY: Pursuing the radioactive issues here for a second. I would like to ask Phil (Coram), what do youthink the role of any other state agency, such as HRS, might be in the future as far as regulating or notregulating any possible radiological issues with gypsum stacks.

CORAM: HRS is the state agency responsible for regulating the handling of radioactive materials. Ourdepartment simply gets involved when we are looking at groundwater and compliance with groundwaterstandards. But as far as human health impacts or occupational exposure, it’s the the Department of Health andRehabilitative Services that has the primary regulatory role.

GARRITY: As a follow-up, then, to Commissioner Young’s question, if EPA were to change their regulationswould the companines still need permission from HRS for these issues or do you think that they would besetting separate regulations or do you think they would just accept the change in EPA’s regulations.

CORAM: It is my understanding that there are only a few of the materials that are disposed in gypstacks thatare actually regulated by HRS. Scale from the filters, is one of those materials. I don’t believe that PG in andof itself exhibits enough redioactivity to be reglated by HRS. A few of the materials that are disposed of in aPG stack mainly scale from the filters and I think that’s about it.

WIEGEL: (To Rubin) I think in your presention, much of it concerns the engineering problems and the costsassociated with expanding an existing gypsum stack. If, in fact, the regulations were changed so that PG couldbe used either in agriculture or construction or both, would this then necessitate additional tremendous capitalinvestments on the part of the industry or is that something that could be relatively easily done without cost?

RUBIN: Ron are you talking about taking existing phosphogypsum from the stacks and utilizing it? I am notsure I understood the question.

WEIGEL: I guess I would first visualize new phosphogypsum being used, but perhaps eventually that whichhas already been deposited in the stacks as being consumed for some beneficial use.

RUBIN: Well, the cost of transporting the PG from the stacks is significant, but by the same token, if it has auseful purpose, I think the economics would have to stand on their own, as far as utilizing the material.

WEIGEL: So that you would, in essence, just add to what you have currently spent for your expanded gypsumstack.

RUBIN: As far as taking the gypsum and then utilizing it somewhere?

14

WEIGEL: Correct. You would have to provide some technique for reclaiming the gypsum, including whatevervehicle for transport and that sort of thing.

RUBIN: You would essentially be mining the gypsum stack as we did when we borrowed, so to speak, gypsumfrom our existing stack to place on top of the liner in the expansion area, and I would visualize that type ofoperation. I think you would probably be better off mining existing gypsum than trying to treat gypsum rightout of the plant, but I think we would have to take a look at both sides of that.

OHANIAN: I know that some of you in the audience are eager to ask questions, but the way we are conductingthis is that the main interaction is between the speakers and the policy panel. If you really have any hotquestions you want to ask, perhaps you can write them down and bring them up here and we will see if we canwork them in.

COLEMAN: Jack, I received one of those questions. We are going to have a problem in handling becausemany of the questions will come in for instance, asking about risks. If we as panelists bring those questionsforward, perhaps those people assessing the risks, or the capability of, for instance, centrifugal separation, cananswer, during their speeches, some of these questions. Otherwise, our panelists are going to have todetermine, as experts, which questions go where.

OHANIAN: They should go to each specific panel as they come up. Otherwise, we will never get through.

15

APPLICATION RATES OF PHOSPHOGYPSUM IN AGRICULTURE

BY

MALCOLM E. SUMNERUNIVERSITY OF GEORGIA

Author: Malcolm E. Sumner, University of Georgia

Dr. Sumner is currently Regent’s Professor and Coordinator of the Environmental Soil Science Program at theUniversity and concurrently holds the title of Honorary Professor, University of Newcastle-upon-Tyne, UK. Hehas been a professor with the University of Georgia since 1977, with prior teaching assignments at theUniversities of Natal (South Africa), Missouri, Wisconsin, and Newcastle-upon-Tyne (UK). Dr. Sumner is aninternationally recognized authority in the fields of soil science and crop nutrition, and he has authored fourbooks and over 180 technical papers.

Dr. Sumner holds bachelor’s and master’s degrees from the University of Natal (South Africa) and a Ph.D fromthe University of Oxford (UK).

* * * * * * * *

Preamble

In 1992, the Environmental Protection Agency (EPA) banned the use of phosphogypsum containing more than10 pCi “‘jRa g-’ for application to soils (Environmental Protection Agency, 1992). This ban was based oncalculations of risk assessment on the assumption that phosphogypsum would be applied to a given soil at a rateof 2700 lb ac-’ biennially for 100 years. As will be shown in this report, this assumption is incorrect. TheFertilizer Institute unsuccessfully challenged the Final Rule made by the EPA who contended that thisapplication rate truly reflected the likely usage of phosphogypsum in agriculture.

Introduction

Gypsum is used in agriculture for the following purposes:. as an ameliorant for sodium-affected (sodic) soils which occur mainly in arid areas and is therefore of

minor interest in this report,. as a source of the nutrients calcium (Ca) and sulfur (S) required by all crops,. as an ameliorant for the subsoil acidity syndrome which commonly afflicts soils in the Southeast, and. as an ameliorant for crust and seal formation at the soil surface, a condition commonly encountered in

the sandy textured soils of the Southeast.

This report has been prepared for the Florida Institute of Phosphate Research (FIPR) with the followingobjectives:

. to independently assess the published experimental evidence on gypsum use in agriculture in theSoutheastern United States and in Florida in particular, and

. to compare the gypsum application rate assumed by the EPA in their calculations to actual field practiceby computing both on a lb ac* yr’ basis.

17

To achieve these objectives, a thorough literature review was undertaken in an attempt to survey all citations sothat the final outcome cannot be contested on the basis of a limited data set.

Calcium (Ca) Requirements of Crops

The following are the essential roles Ca plays in the nutrition of all plants:. serves vital functions in the development of cells,. is essential for membrane integrity and functioning of hormones,. aids in the signalling of environmental changes, and. partially offsets the toxic effects of aluminum (Al).

The amounts of Ca required to be present in soil by various crops can differ widely and in circumstances wheresoil Ca levels are low, gypsum is often used to remedy this deficiency.

Peanuts. The major crop in the Southeast for which Ca is most critical, is the peanut (Arachis hypogea) whichhas received most attention in the literature. The responses obtained in the field have served as the basis for thedevelopment of State Recommendations by the Cooperative Extension Service for the application of gypsum topeanuts. Research has clearly demonstrated that substantial benefits are to be derived from rotating peanuts withother crops which are not susceptible to peanut pests. This is by far the cheapest and most effective way ofcontrolling peanut pests in the field. Consequently, the Cooperative Extension Service in all southeastern statesadvises farmers to rotate peanuts with other crops on a routine basis. Rotation of peanuts in a 2- or 3-yearrotation is practiced by over 75 % of the farmers in the Southeast. Therefore, the gypsum application ratesrecommended by the various states in Table 1 must be divided by 2 or 3 depending in whether peanuts appearevery other year or every third year in the rotation. Rotational considerations do not appear to have been takeninto consideration in the EPA’s Ruling. Indeed, very few peanut farmers would ever be foolish enough to plantpeanuts continuously on the same piece of land. As the literature review undertaken in this treatise indicates thatthese application rates are based on sound scientific data, they should be used as the basis for calculating anannual gypsum application rate. This aspect of peanut production was not apparently considered by the EPA inarriving at the Final Rule on Phosphogypsum.

On a whole field basis (broadcast application), the highest gypsum rate recommended for peanuts in theSoutheast is 1720 lb gypsum a&. Taking the most conservative approach assuming that peanuts are grown in atwo-year rotation (practiced by only one-third of peanut farmers on average), the maximum recommended rateon an annual long-term basis would be 860 lb ac-1 yr-‘. Because there is substantial financial gain to be achievedby growing peanuts in a three- over a two-year rotation, many farmers follow a three-year rotation systemwhich would reduce this figure to 573 lb gypsum ac-’ yr-‘. Thus by comparison with the maximum rate at whichgypsum would ever be applied in practice on a long-term basis to a given field (860-573 lb gypsum ac-’ yr-‘),the figure of 1350 lb gypsum ac-’ yr-’ used by the EPA in their risk assessment calculations is too high by afactor of between 1.56 and 2.35.

However in many cases, farmers usually band place gypsum because this is much more economical as onlybetween l/3 and l/2 of the amount is required. As a result the most likely rates at which gypsum would beapplied to most production fields in any one year would be between 250 and 860 lb gypsum ac-’ yr’ (Table 1).Consequently, the actual long-term rates would lie between 125 and 430 for a two- and 83 and 267 lb gypsumac-’ yr-’ for a three-year rotation system. Thus in the most likely case, the EPA figure overestimates actual fieldpractice by a factor between 3.1 and 16.3.

18

Table 1 Recommended gypsum rates for peanuts in the Southeast (Hodges et a1.,1994)

State Type

Alabama Runner

Florida Virginia

Runner, Spanish-

seed

Georgia”

North Carolina

South Carolina

Virginia

Runner, Spanish

Virginia

Runner, Spanish-

seed

Runner, Spanish

Virginia

Virginia

Runner, Spanish

Virginia, seed

Soil Ca

Low 250”

LOW 500

Med 250

All 800

All 400

Low 400 800 449 896

All

All

LOW 344-430 688-860 386-483 772-965

All 600-800 1200-1600 673-897 1346-1795

All 600-800 1200-1600 673-897 1346-1795

All 400-500 800-1000 449-561 898-l 122

All 600 900-1500 673 1010-1683

lb ?C-' kg ha-’

Band’ Broadcast Band Broadcast

688-860

344-430

Gypsum Re ommendation

1600

800

1376-1720 772-956 1544-1913

688-860 386-483 772-965

280

560

280

898

449

1795

896

t Band widths vary by State: Alabama = 30 cm (12 in ); Florida, Georgia, North Carolina, South Carolina = 45 cm (18 in); Virginia = 50 cm (20 in)

P Values for Georgia have been converted from Ca to equivalent pure CaSO, * 2H,O * When lime is applied

19

Assuming that half the farmers would broadcast phosphogypsum in a 2-year rotation and half would band placephosphogypsum in a 3-year rotation, the maximum average rate over all situations would be (860+267)/2 =563 lb gypsum ac-’ yr-‘. The maximum, most likely and minimum rates of gypsum application are presentedbelow:

. Maximum Rate: 600 lb phosphogypsum ac? yr-’

. Most Likely Rate: 125-430 lb phosphogypsum ac-’ yr-’

. Minimum Rate: 0-83 lb phosphogypsum act yr-’

Tomatoes and Other Vegetable Crops. Tomatoes and peppers also have a definite requirement for Ca toreduce the incidence of blossom-end rot that can take a heavy toll on the quality of the crop. However in mostcases, leaf sprays of Ca salts in minute amounts are highly effective and seldom if ever would gypsumapplications be made to the soil. Only two States (Georgia and Tennessee) have gypsum recommendations forsoil application ranging from 430 to 860 lb a&. Because vegetable crops are highly susceptible to a wide rangeof diseases, rotations with other more resistant crops would always be practised by farmers forphytopathological control. Consequently, the most likely long-term annual rates would range between 215 and430 for a two- and 143 and 287 lb ac-’ yr-’ for a three-year rotation. These values are between 3.1 and 9.4times lower than the assumed EPA figure of 1350 lb ac-’ yr-‘. The maximum, most likely and minimum rates ofgypsum application are presented below :

. Maximum Rate: 430 lb phosphogypsum ac-’ yr-’

. Most Likely Rate: 200-300 lb phosphogypsum ac-’ yr-’

. Minimum Rate: 0-143 lb phosphogypsum ac-’ yr-’

Sulfur Requirements of Crops

Sulfur (S) which is an essential element for plant growth, is a constituent of a number of amino acids and istherefore required for protein synthesis. Crops take up between 10 and 20 lb S ac-’ for normal growth.Extensive experimentation has been carried out in all States in the Southeast to determine the rate of soil-appliedS for optimal crop production, and forms the basis of the State Recommendations complied by the CooperativeExtension Service. These recommendations which have been converted to an equivalent gypsum basis, aresummarized in Table 2.

20

Table 2 Recommended rates of gypsum application to crops in the Southeast to supply the essential element sulfur (S)

State

Alabama

Florida

Georgia

North Carolina

South Carolina

Crop

All

Agronomic, grass

All

Corn, small grains, cotton, tomato, bermudagrass

All

Gypsum Rate (lb ac-‘)

54

80-108

54

108-161

54

Thus, the maximum recommended gypsum rate for any crop is 161 lb a? yr“ which is more than eightfold lower than the rate (1350 lb ac-’ yr’) assumed by the EPA in their risk assessment calculations. The maximum, most likely, and minimum rates of gypsum application as a source of S are presented below:

b Maximum Rate: 161 lb phosphogypsum ac-’ yr’

l Most Likely Rate: 50-80 lb phosphogypsum ac-’ yr-’

b Minimum Rate: 0 lb phosphogypsum ac-’ yr-l

Gypsum for Subsoil Acidity Amelioration

Only a limited amount of research has been conducted in the Southeast to study the beneficial effects of gypsum on soils with acid subsoils where root penetration is limited. Most of the research has been confined to Georgia where a single 2.2-4.4 t gypsum ac-’ application has resulted in substantial yield responses which have been sustained over a long period of time. Because the longevity of this effect is in excess of 10 years, the recommended rate on an annual basis would be 400-800 lb gypsum ac-’ yr-’ which is at least 1.7-fold less than the assumed EPA value. At present, very few farmers have attempted this amelioration strategy and because of the high initial cost in excess of $175 a&, only very limited acreage devoted to highly remunerative crops is likely to be used in this cropping system in the future. The maximum, most likely, and minimum rates of gypsum application for the amelioration of subsoil acidity are presented below:

. Maximum Rate: 800 lb phosphogypsum ac-’ yr-’

. Most Likely Rate: 400 lb phosphogypsum ac” yr’

. Minimum Rate: 0 lb phosphogypsum ac-’ yr-’

21

Gypsum as an Ameliorant for Soil Physical Properties

Reclamation of Sodic Soils. Although sodic soils which are common in arid areas, do not occur to any appreciable extent in the Southeast, a brief overview of the gypsum requirements of these soils was undertaken because the EPA’s Final Rule incorporated gypsum application rates for this purpose. The applications rates used in determining the Final Rule were based on commonly used rates and did not take the total amount required for reclamation into consideration. Based on a review of field reclamation studies, applications of between 7 and 35 t gypsum ac-’ would be required to reclaim the top 20 in (which is sufficient rooting depth for most crops under irrigation) of a highly sodic soil (exchangeable sodium percentage [ESP] =30) . On an annual basis, this would correspond to applications between 140 and 700 lb gypsum ac-’ yr-’ over a loo-year period which is between 2- and lo-fold less than the EPA assumed value. However in certain cases, applications in excess of these amounts have been made to certain soils, but these cases represent the exception rather than the rule.

If the biennial application rate (2700 lb phosphogypsum ac-‘) used by the EPA in arriving at the Final Rule was applied to a sodic soil over a loo-year period, this would amount to an application rate of 68 t ac-’ which is approximately twice the rates commonly used in practice. The maximum, most likely, and minimum rates of gypsum application for the reclamation of sodic soils are presented below:

0 Maximum Rate: 700 lb phosphogypsum ac-’ yr’

. Most Likely Rate: 200-500 lb phosphogypsum ac-’ yri

. Minimum Rate: O-200 lb phosphogypsum a& yr-’

Crusting and Seedling Emergence. Most of the research in the Southeast on this aspect of gypsum use has been conducted in Georgia where, as a result of reduced crusting, substantial improvements in water entry into soils have been obtained, thereby reducing runoff and erosion. Typically, applications ranging between 0.5 and 2 t gypsum ac-’ have proven to be highly successful and currently the Cooperative Extension Service recommends 0.5-l t gypsum ac-’ for this purpose. Such applications are only recommended as an interim measure in the establishment of a permanent vegetative cover on highly erodible soils. Thus, this should be considered as an application that would be made once only or, at the most, once in five years in a no-till system. Relatively few farmers have adopted this technology at present as many consider it to be too expensive. However, if applications are made only over the row, the application rates would be reduced by a factor of 2-3. Thus, the maximum amount of gypsum that would be applied over a loo-year period would not exceed 7-10 t ac-‘. The maximum, most likely, and minimum rates of gypsum application for the amelioration of crusting are presented below:

. Maximum Rate: 200-400 lb phosphogypsum aci yr’

. Most Likely Rate: 100-200 lb phosphogypsum ac-’ yr-’

. Minimum Rate: lo-50 lb phosphogypsum ac-’ yr’

22

Mechanical Impedence. Gypsum applications to the soil surface have been shown to reduce the mechanicalimpedence (resistance to root penetration) of subsoil horizons as a result of improved flocculation of the clay. Asingle 4.4 t ac-’ application of gypsum was sufficient for this purpose and the effect has lasted in excess of 10years giving a long-term application rate of about 800 lb gypsum ac-’ yr- ‘. Because of the high cost involved inthe initial gypsum application, no farmers have yet attempted to use this strategy. The maximum, most likely,and minimum rates for this use are presented below:

. Maximum Rate: 800 lb phosphogypsum ac-’ yr-’

. Most Likely Rate: 400 lb phosphogypsum ac-’ yr-’

. Minimum Rate: ? lb phosphogypsum ac-’ yr-’

Environmental Impacts Associated with the Agricultural Use of Phosphogypsum

Application of a phosphogypsum with a high 226Ra content (35 pCi g-l) at the maximum rates for the differentuses described above for a 100-year period would result in a maximum cumulative 226Ra concentration of 1.57nCi 226Ra kg-1 of soil (58.0 Bq kg-r) which is much lower than the 5 nCi U6Ra kg-’ (185 Bq kg-1) considered tobe the upper limit of a safe range. Where phosphogypsum has been used as a source of Ca or S for crops,radiation added to the soil has, in all cases, not significantly increased native background levels. Even where asingle rate of 4.45 t phosphogypsum (17.6 pCi 226Ra g“) ac” was applied, no significant increases in ‘14Pb, ‘r4Bi,or 226Ra could be detected anywhere in the profile of two different soils to a depth of 3 ft, 5 years afterapplication. No significant differences in plant uptake of these radionuclides could be detected due tophosphogypsum treatment. However in a leaching experiment on a very sandy soil, elevated 226Ra concentrationswere found in the leachate but these concentrations were well below the maximum allowed in drinking water.

Based on the scientific data, the conclusion can be drawn that there should be little concern associated with theuse of phosphogypsum containing more than 10 pCi “6Ra g-’ provided that Cooperative Extension Serviceapplication rates are used.

Conclusions

All the soundly based experimental data strongly suggest that the phosphogypsum rate of 1350 lb ac-’ yr’ for100 years used by the EPA as the basis for formulating the Final Rule on phosphogypsum use, is too high. Amore appropriate maximum figure would be in the range 600-800 lb gypsum ac’ yrl with the most likelyapplication rate lying in the range 100-400 lb gypsum ac“ yr-‘.

23

GYPSUM AS A SOIL AMENDMENT IN CALIFORNIA

BY

ROLAND D. MEYERUNIVERSITY OF CALIFORNIA - DAVIS

********

Author: Roland D. Meyer, Extension Soils Specialist, University of California - LAWR Dept., Davis, CA.

Dr. Meyer has been Extension Soils Specialist at University of California - Davis, LAWR Department since1973. Prior to joining UC-Davis, he served as Area Agronomy Specialist with the University of MissouriCooperative Extension and worked in fertilizer and agricultural chemical sales in North Central Nebraska withFarmland Industries, Inc. Since coming to UC-Davis, his research and extension activities have concerned theefficiency, economics and environmental impacts of fertilizer application to California crops. More recently hehas been involved in evaluating the possible utitilztion of various waste products such as fly ash and bottom ash,animal manures, sewage sludge and composts of these and other materials as nutrient sources and soilamendments in agriculture, forestry and landscape settings.

Dr. Meyer has bachelor’s and master’s degrees from the University of Nebraska and earned the Ph.D. degree inAgronomy from Iowa State University.

Gypsum is used for several purposes in California agriculture. The largest volumes are used in one or twomanners, for the reclamation of salt affected soils and improving water infiltration in soils. The third largest usewould be as a nutrient source for sulfur. Smaller volumes of gypsum are used in the amelioration of highmagnesium soils and acidic soil conditions. The purpose of this presentation is to describe the use of gypsum inthe reclamation of soils and improving water infiltration where the highest rates per unit of land area arenormally found.

The gypsum used in agriculture originates from two primary sources, mined gypsum and the by-product fromthe manufacture of phosphate fertilizers called phosphogypsum. For the period from 1977 through 1990,phosphogypsum accounted for less than 2% of the total use in 1977, rising to nearly one third during the period1983-1986 and down to less than 10% in 1990 (Figure 1). This use pattern was a reflection of the availability ofphosphogypsum from the phosphate manufacturing industry. Recent implementation of gypsum injectionequipment developed for drip and other low flow irrigation systems has necessitated the introduction of veryfine gypsum, 99-100% smaller than 0.15 mm, 93-97% finer than 0.07 mm, and 3-78% finer than 0.04 mm.

In the reclamation of salt affected soils, particularly those having high sodium concentrations, gypsum is used asa source of calcium to replace the sodium. The process of reclamation usually begins by establishing adequatedrainage which may involve the installation of underground tile drainage where natural soil drainage isinsufficient. Additional steps involve testing the soil on some type of grid system to identify the degree ofreclamation necessary followed by an initial rate of 3-5 tons gypsum application per acre before fall rainfall orirrigation begins. When sufficient leaching has occurred, a more salt tolerant crop such as barley is planted.Soils from the areas of poor barley growth are retested to develop additional gypsum recommendations which

25

are usually in the 1-2 tons per acre range. Continued leaching with irrigation and winter rains along withadditional applications of 1-2 tons gypsum per acre may be necessary before uniform crop growth is establishedthroughout the field. Average application rates for the first ten to fifteen years are about one ton gypsum peracre with a range of 0.5 to 1.5 tons per acre. Rates of gypsum application will be considerably less after thereclamation is well underway with rates averaged over a 50 year time frame having a minimum and maximumof 0.2-0.7 tons per acre per year respectively.

The second major use of gypsum in California agriculture is the addition to very pure (EC < 0.2 dS/m)irrigation water to improve the infiltration in soils. This may in fact represent the highest use of gypsum on aunit soil area basis with broadcast rates on occasion exceeding one ton per acre per year. Water originatinglargely from snowmelt in the Sierra Mountains is of very pure quality and unless blended with higherconcentration divalent calcium and magnesium salts from groundwater requires the addition of gypsum toprevent the soil surface from sealing. Various techniques have been used over the past 50 years to address thisproblem. Gypsum was applied to the soil surface at rates of 0.25 up to as much as 1 ton per acre every year ortwo. To increase the salt concentration of the water, large concrete chambers 6-8 feet wide and 10-20 feet longwere used to contain the gypsum while the irrigation water was allowed to pass over the gypsum and dissolveappropriate amounts. Growers having flood or furrow irrigation systems currently use broadcast or bandedgypsum on the soil surface at the rates mentioned previously. In crops where drip or other low volumeirrigation systems are used, the injection of a quality finer grade gypsum is becoming more widely accepted.Rates applied typically range from 0.25-0.75 ton per acre with an average of 0.5 ton per acre each year.

Another common use of gypsum is in the case where soils and/or irrigation water have low to moderate levelsof sodium. Rainfall amounts may be sufficient in some years to provide adequate leaching but significantimprovement in water infiltration or the reduction of sodium levels is desired such that gypsum is applied at therate of 1-2 tons per acre every four or five years. Long term average application rates would be of the order of0.2-0.4 ton per acre per year.

Several areas of the state where alfalfa is the principle crop receive gypsum at the rate of 0.15 to 0.25 tons peracre every two years to provide adequate amounts of the plant nutrient sulfur. The rapid growth response fromthe readily available sulfate-sulfur allows it to compete economically with elemental sulfur which is less costlyper pound of sulfur but has a much longer term release pattern.

The north coast of California and several other areas where serpentine parent materials give rise to soils havingsoluble calcium:magnesium ratios of less than 1:2 represent another use of gypsum in agriculture. Plant growthis dramatically increased when calcium from gypsum is increased in the soil and calcium:magnesium ratios aregreater than 1:1. Rates on the order of 10 to 20 tons per acre as a one time application with a follow uptreatment of 5 to 10 tons per acre after approximately 40 years could result in a 50 year average high use of 0.5to 0.6 tons per acre per year.

26

References:

Oster, J. D., I. Shainberg and I. P. Abrol. “Reclamation of salt-affected soil. ” In Soil Erosion, Conservation and Rehabilitation, M. Agassi (ed.) pp 315-352. New York: Marcel Dekker, Inc., 1995.

Fertilizer Materials Tomrage Reports. 1977-1990. California Department of Food and Agriculture, 1220 N Street, P. 0. Box 942871, Sacramento, CA 94271-0001.

Figure 1. Gypsum use in California agriculture (in thousands of tons).

1980 1983 1986 1989 Year

\Phosphogypsum l ++ Gypsum

27

THE ECONOMIC BENEFIT OF PHOSPHOGYPSUM USE IN AGRICULTURE IN THESOUTHEASTERN U.S.

BY

GREG TRAXLERAUBURN UNIVERSITY

*******

Author: Greg Traxler, Associate Professor, Department of Agricultural Economics and Rural Sociology,Auburn University

Dr. Traxler has dealt with the economics and statistics of agricultural cropping since completing his Ph.D. in1990, and he has published numerous articles in various agricultural economic journals on crop managementpractices.

Dr. Traxler holds a bachelor’s degree from the University of Portland, a master’s degree from the University ofMinnesota and the Ph.D. degree from Iowa State University.

********

Introduction

Agriculture accounts for about 5 percent of the nearly 30 million tons of gypsum used in the United States eachyear. This report estimates the economic benefit of removing restrictions on phosphogypsum use in agriculturein the Southeast.

Size and Organization of the U.S. Phosphate Industry

A total of 14 companies produced phosphate in the United States in 1993. About 85 % of the U.S. production,or 35 million tons, is accounted for by the six companies located in central Florida and one in North Carolina.The U.S. also imported aproximately 850,000 tons annually during this period. The U.S. has no duties or tariffson fertilizer imports.

Gypsum production

There are no operating gypsum mines in the Southeast. Gypsum used in the Southeast is either byproductgypsum or is imported mined gypsum. Byproduct gypsum accounts for about three percent of the gypsum usedin the U.S. Of the two major sources of byproduct gypsum, the desulfurization of stack gas in thermalpowerplants provides the largest share of byproduct gypsum. Despite an overall rise in byproduct gypsum sales,phosphogypsum usage has fallen by 50% since me 1990 EPA ruling limiting its use. An average of 207,000tons of phosphogypsum were used in 1988-90, while the 1990-92 average is just 102,000 tons in 1993(Llewellyn). Over the same period, the share of phosphogypsum in total byproduct sales fell from approximately30 percent to 10 percent.

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Gypsum use in agriculture

A total of nearly 1.5 million tons of gypsum, including mined gypsum and byproduct gypsum, were used inagriculture in 1994 (TVA). Agricultural use accounts for about 5 percent of the total of nearly 30 million tonsof gypsum used in the United States; construction uses account for 90 percent of total use. Agronomists havebeen unable to detect differences between the agronomic effects of phosphogypsum and mined gypsum (Mullinsand Mitchell, Sumner).

The uses of gypsum in agriculture fall into three main categories (Sumner): 1) as a source of calcium for peanutproduction 2) as a source of sulfur for vegetable crops and forages 3) as an ameliorant for soil sodicity, crustingand subsoil acidity problems. Only 8,000 tons of sulfur from all sources were directly applied in the region in1994 (TVA). The use of gypsum to reclaim sodic soils occurs primarily in irrigated agriculture, especially inCalifornia, but occurs very rarely in the Southeast. By far the most commercially important use of gypsum inthe Southeast at present is as a source of calcium for peanut production.

An average of 1.29 million acres of peanuts are planted in the six southern states of Alabama, Florida, Georgia,North Carolina, South Carolina, and Virginia. The Southeast’s “peanut belt” is centered about 150-200 milesfrom Florida’s main phoshorus mining areas. About 80 percent of U.S. peanut production takes place within a100 mile arc around the juncture of the Georgia, Florida and Alabama borders. Georgia accounts for more thanhalf of the U.S. peanut area.

The value of gypsum as a source of Ca for peanut production has been recognized since the 1940’s (Sumner).Among Southeastern states, recommended application rates range from 250 lb ac-’ to 860 lb ac-’ for bandedapplication and from 688 lb ac-’ to 1720 lb ac-’ for broadcast application (Sumner).

An average of 198,626 short tons of gypsum are used in agriculture in Georgia, Florida, and Alabama eachyear (TVA). Virtually all of this gypsum use is for peanut production. Personnel at the USDA national peanutresearch laboratory collected information on input from a random sample of 84 peanut farmers in 1993 (Lamb).Forty-six percent of surveyed farmers applied gypsum. Of farmers using gypsum, the average application ratewas 879 lb/ac. Ninety-five percent of surveyed farmers used an application rate of 1,000 lb/ac or less, 99% ofapplication rates were 1,500 lb/ac or less, and the highest observed application rate was 3900 lb/ac. Theaverage gypsum expenditure was $17.44 per season, and the average farm price was $40.00/ton..

The Potential Economic Benefit from Phosphogypsum Use in Agriculture

The net economic benefit from allowing unrestricted use of phosphogypsum in agriculture in Georgia, Floridaand Alabama was calculated within the framework of economic welfare analysis. Welfare analysis, which is aform of benefit/cost analysis, is the most common method used by economists to quantify the costs and benefitsof changes in government policies. Just, Hueth and Schmitz summarize the economic welfare literature whichhas been developed since welfare analysis was first used by Ricardo in the early nineteen century. Welfareanalysis is a tool that is relatively easy to understand and apply as well as being theoretically justified.

Calculating the net benefit of unrestricted phosphogypsum use is quite straightforward. The most importantparameters needed to calculate welfare changes are: a) the reduction in the gypsum price that will occur as newsources of phosphogypsum enter the market, b) the quantity of gypsum used in agiculture, and c) gypsum(phosphogypsum) supply and demand elasticities. Elasticities only have a minor effect on total estimated welfarebut are important in determinig the distribution of welfare changes. In the case of phosphogypsum, becauseagriculture represents such a small proportion of total gypsum use, a change in the use of gypsum in agriculturewill have a negligible effect on the price of gypsum. This implies that the supply of phosphogypsum can beassumed to be perfectly elastic and all benefits, or surplus increases, will accrue to farmers.

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Because phosphogypsum is a byproduct of the competitive phosphorus industry, it is expected thatphosphogypsum will be supplied at a zero price F.o.b. mines in central Florida. Each year the Florida phoshateindustry adds some 30 million tons of phosphogypsum to the existing 600 million ton inventory (Llewellyn).The annual increment to stockpiles is 150 times the current total agricultural gypsum use in the Southeast. Thehuge phosphogypsum surplus and the significant storage costs imply that it is in the best interest of the industryto supply at any price below the marginal storage cost. In fact, it is not inconceivable that phosphorus producerswould pay for phosphogypsum to be removed.

The formula for calculating the welfare change. or net benefit, is:

(1) Change in welfare = QJP + 0.5APAQ

where Q,, is current level of gypsum use, AP is the change in price of gypsum with phosphogypsum restrictionsremoved, and AQ is the change in gypsum consumption as the price falls. The AQ is based on an assumedelasticity of demand for gypsum of -0.2. The first term in (1) is simply the price change times the currentquantity of gypsum used. The second term accounts for the small increase in gypsum use which will occur asthe price falls. Equation (1) is the annual benefit of the fall in the price of gypsum. Since this is expected to bepermanent price reduction, the total financial benefit is the net present value (NPV), which is the discountedsum of the annual benefit amounts for all future years.

The Tennessee Valley Authority (TVA) reports average annual gypsum use quantities for 1985-94 of 155,200short tons in Georgia, 43,284 in Florida and 158 tons in Alabama. No published studies have estimatedelasticity of demand for gypsum, but several reported elasticity estimates for phosphorus and nitrogen arereported (Larson and Vroomen, Roberts). A value of q=-0.2 was used in this study.

Some uncertainty exists about the equilibrium gypsum price when phosphogypsum restrictions are removed.Conservative estimates of the new gypsum price were used in the benefit calculations. Phosphogypsum cancurrently be purchased at White Springs, Florida from Occidental Chemical Agricultural Products for$l0.00/ton. It is assumed that with the entry of new phosphogypsum suppliers in central Florida, Occidentalwill be forced to reduce its price to meet this competition. It is assumed that central Florida suppliers will bewilling to supply phosphogypsum at a zero price F.o.b. central Florida. The delivered farm price will then bedetermined by the transportation price of $7.00/ton/100 miles. Because Occidental is located approximately 100miles nearer than other suppliers to the peanut growing areas, it will not be forced to supply phosphogypsum ata zero price, but rather will need to meet the effective North Florida price of other phosphogypsum suppliers of$7.00 (i.e. the cost of trasportation from central Florida to White Springs). The result is that the deliveredgypsum price to Georgia, Alabama and north Florida peanut growing areas can be expected to fall by aminimum of $3.00/ton.

Because of the uncertainty involved with predicting this future gypsum price, benefit calculations were doneusing price assumptions ranging from the minimum expected price reduction of $3/ton up to $10/ton reduction.The annual net benefit is estimated to be $609,284 under the $3/ton price assumption. The net present value ofthis annual benefit flow is $11,942,236 using a 3% real discount rate. If prices fall by $5.00/ton the annualbenefit will be $1,055,199 and the NPV will be $20,682,356. Finally if prices should fall by $10.00/ton theannual benefit will be $2,482,820 and the NPV will be $48,664,368.

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Summary

Economic welfare analysis was used in this study to estimate the benefit of unrestricted use of phosphogypsumin agriculture in the states of Georgia, Florida and Alabama. An average of nearly 200,000 tons of gypsum areused in agriculture in these three states each year, primarily as a source of calcium for peanut production.Forty-six percent of peanut producers in Georgia apply gypsum. Of farmers using gypsum, the averageapplication rate is 879 lb/ac. Ninety-nine percent of peanut producers in Georgia apply 1,500 lb/ac or less.Using conservative economic assumptions, the annual net benefit from removing the restrction on gypsum use inagriculture.is estimated to be between $609,284 and $1,055,199. The net present value of this annual benefitflow would be between $11,942,236 and $20,682,356.

References

Davis, L.L. “Gypsum.” In Minerals yearbook. U.S. Bureau of Mines, Dept. of the Interior. 1993.

Just, R.E., D.L. Hueth, and A. Schmitz. Applied welfare economics and public policy. Englewood Cliffs, N.J.:Prentice-Hall. 1982.

Lamb, M. “Economic Analysis of Planning, Management and Marketing Peanuts in the Southeast U.S.”Unpublished Ph.D. dissertation, Auburn University. 1995.

Larson, B.A. and H. Vroomen. “Nitrogen, phosphorus, and land demands at the U.S. regional level: a primalapproach.” Journal of Agricultural Economics. 42 (1991):354-64.

Llewellyn, T.O. “Phosphate rock.” In Minerals Yearbook. U.S. Bureau of Mines, Dept. of the Interior. 1993.

Mullins G.L. and C.C. Mitchell. Use of phosphogypsum to increase yield and quality of annual forages.Publication No. 01-048-084. Bar-tow, FL: Florida Institute of Phosphate Research, 1990.

Roberts, R.K. “Plant nutrient demand functions for Tennessee with prices of jointly applied nutrients.” SouthernJ. Agric. Econ. 18 (1986):107-112.

Sumner, M.E. “Use of calcium and sulfur as nutrients for crops in Florida: Reconciliation of literature reviewwith EPA’s final rule on phosphogypsum. " report prepared for Florida Institute of Phosphate Research. 1995.

Sumner, M.E. Gypsum as an ameliorant for the subsoil acidity syndrome. Publication No. 01-024-090. Bartow,FL: Florida Institute of Phosphate Research, 1990.

Tennessee Valley Authority. Various years. Commercial fertilizers. TVA, Muscle Shoals. AL.

32

PHOSPHOGYPSUM AS A VALUABLE AND INEXPENSIVE SOURCE OFNUTRIENTS FOR CROPS

BY

J. E. RECHCIGL1, C. E. ROESSLER2, I. S. ALCORDO1 and R. C. LITTELL3

********

Presenter: Jack E. Rechcigl, Associate Professor of Soil and Environmental Studies, University of Florida

Dr. Rechcigl has been on the faculty of the University of Florida since 1986 and has published extensively inthe fields of soil fertility, environmental quality, and (agricultural runoff) water pollution. A large part of hisresearch program has included the environmental impacts of using industrial waste products (includingphosphogypsum) in agriculture. He has published extensively and has edited several monographs onenvironmental quality, and is a well-traveled international speaker.

Dr. Rechcigl has a bachelor’s degree from the University of Delaware and the master’s and Ph.D. degrees fromthe Virginia Polytechnic Institute and State University,

********

Sulfur deficiencies in plants have been reported in more than 35 states, including Florida. Although sulfur isusually considered a secondary plant nutrient, it still needs to be viewed as one of the major nutrients essentialfor crop growth, along with nitrogen, phosphorus and potassium. Sulfur is required by plants for the synthesisof certain amino acids which are required for protein production. Thus, if sulfur is limiting, forage quality, aswell as quantity, will be reduced. In fact, sulfur deficiencies are often confused with nitrogen deficiency. In lesssevere cases of sulfur deficiency, visual symptoms may not always show up, while crop yield and quality areaffected.

Until recently, little attention has been given to the need for sulfur fertilization in Florida and other parts of thecountry. This is understandable since in the past low analysis fertilizers contained sulfur impurities sufticient tomeet the nutrient requirements for forage production. However, today fertilizer manufacturing technology hasbecome highly advanced and consequently high analysis fertilizers, such as triple super-phosphate anddiammonium phosphate, are free of sulfur impurities. As a result, sulfur deficiencies are becoming morepronounced and widespread throughout the world. Coarse textured soils, such as those commonly found inFlorida, may also exhibit sulfur deficiencies because of their very low nutrient holding capacity.

It is important to note that sulfur fertilization will increase yields and quality of crops only if the plants aredeficient in sulfur. The sulfur status of a crop is best determined by having a plant tissue sample analyzed forsulfur which is more reliable than a soil test. For grasses, the level of sulfur in the plant tissue should rangefrom 0.2-0.5 percent. If the level of sulfur falls below 0.2 percent, it is indicative of sulfur deficiency and thegrass should thus respond to sulfur fertilization.

1Range Cattle Research and Education Center, IFAS, University of FLorida, Ona, FL 338652Dept. of Environmental Engineering Sciences, University of Florida, Gainesville, FL 326113Dept. of Statistics, IFAS, University of Florida, Gainesville, FL 32611

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Over the years, we have demonstrated that addition of sulfur can increase production of harvested forages, suchas bahiagrass (Paspalum notatum L.), by as much as 25 percent and protein content by 1.2 percent. In thesestudies, the sources of sulfur were ammonium sulfate and potassium sulfate which are relatively expensive.Bahiagrass, which is an important forage crop in Florida, is grown on nearly 2.5 million acres annually,exceeding production of all other improved grasses combined. To provide sulfur for this size of land would be aconsiderable expense.

There is a need to find alternative economic sources of sulfur which would be more affordable to growers thantraditional sulfur fertilizers. Phosphogypsum (CaSO,), a by-product of the wet-acid production of phosphoricacid from rock phosphate, is a potential low cost source of sulfur and calcium for forages and other crops. Untilnow, phosphogypsum has had little commercial use because it contains low levels of radium (8-30 pCiRa-226/g), raising concern over its potential harmful effects. In Florida alone, there are more than 700 milliontons of phosphogypsum stored in waste stacks, with 30 million tons being added to the stacks annually. In theentire country the total amount of phosphogypsum in stacks is estimated at seven billion tons.

Experimental Design

Over the past six years, we have evaluated the agricultural and environmental impact of phosphogypsum use onforages grown in Florida. This paper discusses results of a part of that study from 1990 to 1992, dealing withthe effects of phosphogypsum, applied at agronomic rates, on bahiagrass and the environment, at the Universityof Florida Range Cattle Research and Education Center at Ona. Results dealing with the environmental effectsof phosphogypsum will be discussed in our subsequent paper.

Four phosphogypsum rates of 0, 0.2 (applied annually), 1.0, and 2.0 tons/acre (both applied once in 1990) wereapplied to established bahiagrass plots, located on a Myakka fine sand soil. Bahiagrass forage was harvestedmonthly from May until December in order to assess the influence of phosphogypsum on forage production andquality. Soil samples were collected annually to a depth of 3 feet. Water samples were collected after eachheavy rain to a depth of 4 feet. Forage, soil, and groundwater samples were analyzed for various nutrients,including calcium, sulfur as well as fluoride.

Results and Discussion

Forage Yield. Regardless of the rate or time of application, phosphogypsum addition tended to increaseregrowth and mature (hay) bahiagrass yields by approximately 20 percent (Figure 1) during 1991, 1992, andover the 3-year period. Significant increases in regrowth and hay yields were noted for the 0.2 ton/acre as wellas at higher rates, for at least two years, and over the 3-year period for all rates. Other studies have also shownthat addition of phosphogypsum, mined gypsum, or other sources of sulfur can increase forage production whensulfur is deficient (Alcordo and Rechcigl, 1993).

Forage Quality. Phosphogypsum tended to increase crude protein concentration of the mature bahiagrassforage, by as much as 1% in all years and over the 3-year period, and the digestibility, by as much as eightpercentage units (Figures 2 and 3) in some individual harvests in 1990. This is in agreement with other studies,showing that addition of sulfur will increase the nutritive value of forages on sulfur deficient soils. Increases inboth digestibility and protein content of forage are known to increase the weight gains in livestock.Phosphogypsum increased the sulfur and calcium content of the bahiagrass tissue (Figures 4 and 5). The calciumcontent ranged from 0.42-0.60 %, while the sulfur content ranged from 0.18 to 0.40 % for the 0 and 2.0 tonsphosphogypsum/acre treatments, respectively.

Phosphogypsum addition also slightly increased the fluoride content of the bahiagrass tissue, however thecontent was well below the 30 ppm maximum acceptable level for livestock intake (Figure 6). The low levels of

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tissue fluoride found in this study are of some importance since high levels of fluoride may bring about the lossof teeth in cattle.

Conclusions

This study demonstrates that phosphogypsum can increase both the yield and quality of forage grasses, such asbahiagrass. This can, in turn, lead to greater livestock weight gains and increased stocking rates, resulting inincreased profits of ranchers. This could potentially increase cattle production by 10% which could result in anincrease of 36 million dollars a year to the Florida Beef Industry. As the accompanying paper will show, theaddition of phosphogypsum (up to 2 tons per acre) to agricultural land does not appear to present any seriousenvironmental problems. Thus, phosphogypsum may be a viable and an economical source of sulfur andcalcium for forage production.

References

Alcordo, I.S. and J. E. Rechcigl. “Phosphogypsum use in agriculture: a review.” Advances in Agronomy. 49(1993): 55-118.

Alcordo, I. S. and J. E. Rechcigl. “Phosphogypsum and other by-product gypsums.” In Soil Amendments andEnvironmental Quality, J.E. Rechcigl (ed.). pp. 365-425. Boca Raton, FL: CRC/Lewis Publishers. 1995.

35

RADIOLOGICAL ASSESSMENT OF THE APPLICATION OF PHOSPHOGYPSUMTO FLORIDA FORAGE LANDS

BY

C. E. ROESSLER1, J. E. RECHCIGL2, I.S. ALCORDO2, and R.C. LITTELL3

Presenter: Charles E. Roessler, Professor Emeritus, Dept. of Engineering Sciences, University of Florida

Dr. Roessler an extensive background in radiation chemistry and biology (health physics). He has taughtradiation protection, dosimetry, measurements and techniques and has conducted research on radiation doseassessment from medical, occupational and environmental sources. His investigations have included naturally-occurring radioactive materials (NORM), indoor radon, radioactivity of mining-related lands and materials, andphosphogypsum. Dr. Roessler has authored over 50 publications and over 40 technical reports, including“Control of Radium in Phosphate Mining, Beneficiation and Chemical Processing”.

Dr. Roessler has a bachelor’s degree from Mankato State College, a Master of Science in radiation biologyfrom the University of Rochester, a Master of Public Health in occupational health from University ofPittsburgh and received his Ph.D in environmental engineering sciences from University of Florida.

* * * * * * * * * *

Introduction

Naturally-occurring uranium and its radioactive decay series are associated with phosphate mineral deposits.Consequently, the uranium-series member, radium-226, and its radioactive decay products appear in thephosphogypsum (PG) by product of wet-process manufacture of phosphoric acid from phosphate rock. Becauseof this radionuclide content and the concern for human radiation exposure, particularly if PG-treated lands,roads, etc. are converted to other uses in the future, the U.S. Enviromnental Protection Agency has placedstringent restrictions on the use of PG as a resource material (Federal Register 1992).

This paper presents an assessment of the radiological impact of the use of PG to fertilize forage lands. Datawere collected as part of agronomic and environmental studies of PG at the Range Cattle Research andEducation Center of the University of Florida Institute of Food and Agricultural Sciences, Ona, Florida(Rechcigl, et al., 1995a).

1Dept. of Environmental Engineering Sciences, University of Florida, Gainesville, FL 326112Range Cattle Research and Education Center, IFAS, University of FLorida, Ona, FL 338653Dept. of Statistics, IFAS, University of Florida, Gainesville, FL 32611

3 7

Methodology

In the initial phase of this work, PG was applied to forage lands at agronomic rates -- up to 4 Mg/ ha (1.8 tons/acre). When it became evident that radiological effects could not be measured with a consistent degree ofconfidence, a second phase was initiated with additional replication and higher PG rates -- up to 20 Mg/ha (8.9tons/ acre). The purpose of Phase II was to improve the probability of determining quantitative relationshipsbetween PG application rates and radiological parameters and thus provide the necessary factors for projectingthe effect of repeated PC use scenarios.

Table 1 summarizes the experimental conditions for the two study phases. Details of the experimental design,the sampling, analytical, and statistical methods, and the measurement results are presented elsewhere (see Table1 for references). The bases for data reduction, projections, and comparisons are presented in Table 2. Resultsof the measurements were converted to initial effect per unit single application of PG. These factors wereadjusted to the radionuclide concentrations of a reference Central Florida PG. Phase II data were used toestimate future radiological values expected from extended PG use. The projections were made for the case ofPG application to established bahiagrass in Central Florida at the recommended annual rate of 0.4 Mg/ha (0.18tons/acre) with the practice continued for 100 years. For this stage of assessment, it was assumed that theradionuclides accumulated linearly in the soil with successive treatments -- no corrections were made for anyenvironmental loss of radionuclides because data have not been collected over a long enough time to estimatethe loss rate.

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Table 1. Field Studies of PG on Florida Forage Lands -- Experimental Conditions

Purpose

Dates

Crops, Application

Method

Phase I

Scoping; study effects of PG application at agronomic rates

Summer-l 990 - Spring 1993

Two crops: - Established bahiagrass,

surface application; - Ryegrass, Tilled into soil &

cropped each yr for 3 yrs.

Phase II

Develop quantitative relationships by elevated PG application rates

Spring 1993 - Spring 1995

One crou: - Established bahiagrass,

surface application.

Soil Type(s) One soil type for both crops: - Spodosol (Pomona & Myakka sands)

Two soil tvpes: - Spodosol (Myakka) - Alfisol (Malabar)

Treatments, Mglha

(tons/acre)

- 0.0 -- Control - 0.4 (0.18) annually fro 3 yrs. - 2 (0.8), single application - 4 (1.8)) single application

- 0.0 -- Control - 10 (4.5), single application - 20 (8.9), single application

References Rechcigl, et al. 1994a, 1994b; Roessler, et al. 1994.

Rechcigl, et al. 1995b.

Radiological Radon flux -- Radon collection by charcoal canister; submission to commercial Measurements laboratory for analysis by gamma counting.

External gamma radiation exposure and ambient aitborne radon -- Field measurement using electret ion chambers. Radionuclides (“%Ra, 210Pb. “‘PO) -- Field sampling; submission to commercial laboratory for analysis:

* PG . Soil profile + Water (runoff and surficial groundwater) . Forage

Table 2. Bases for Data Reduction, Projections and Comparisons in Tables 3,4, and 5.

Data Source: From field study using PG with “6Ra, 20.6 pCi/g; 210Pb, 30.8 pCi/g; and “‘PO, 24.3 pCi/g.

Radiation/radioactivitv factors and proiections to the future: Scaled to reference PG with =‘jRa, 30 pCi/g; 210Pb, 36pCi/g; and zloPo, 27 pCi/g (from Table 2-3 of US EPA 1992).

Projections for 100th year: Projected cumulative effect and/or concentration in 100th year of annual applications of reference PG at recommended rate of 0.4 Mg/ha (0.18 tons/acre); cumulative addition of 40 Mg/ha (17.8 tons/acre). Without corrections for radioactive decay or any loss of PG or Pg-attributable radionuclides from upper soil layer.

Background: Mean represents overall average for untreated land at Range Cattle Research and Eduction Center. Standard deviation represents the variation among averages for different sites (different sets of plots) at the Center.

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Results and Discussion

Radionuclides in Soil. Calculated additions to the concentrations of PG and radionuclides in the upper 15-cm (6-in) soil layer per unit single application of the reference PG and projections to the 100th year are presented in Table 3. A single treatment at agronomic rates cannot be detected with current analytical methods; after 100 years of annual treatment, the projected added radionuclide concentrations are roughly equal to the existing background at the test sites and within the range of variations seen in Florida lands without enhanced or elevated radioactivity.

Table 3. Soil Radioactivity, Radon Flux, and Gamma Radiation Attributable to PG Treatment of Soil

Parameter, Units

Soil, 15-cm (6-m) Layer? PG Add’n, g PG/g Soil:

226Ra, pCi/g: 210Pb, pCi/g: 21OP0, pCi/g:

Radon Flux, pCi/m2 * s

Addition per Projected for year Mg/ha 100

0.00044 0.018

0.013 0.5 0.016 0.6 0.012 0.5

0.0026 0.11

Background, Mean (Std Dev)

--

0.5 (0.08) 0.7 (0.12) 0.8 (0.40)

0.026 (0.0109) [0.2 (<O.l -1.7)]b

Gamma Radiation, pR/hr 0.015 0.6 5.5 (0.42)

a) PG addition averaged over tilling depth of 15 cm (6 in); soil density 1.5 g/cm3. b) Geometric mean and range observed for other Florida undisturbed, non-mineralized lands.

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Radon Production. A major concern centers around radon-222 (radon), the product of the radioactivetransformation of radium-226. The concern is whether the application of radium-containing PC to land wouldincrease radon production in the soil sufficiently to result in harmful levels of indoor radon in future structuresbuilt on previously-treated land. Surface soil radon flux measurements were performed as an indicator of radonoriginating in the soil.

In Phase I, no statistically-significant radon flux increases were observed for PG applications to bahiagrass up to4 Mg/ha (1.8 tons/acre). Phase II data were used to calculate radon flux contribution per unit of the referencePG and to project to the 100th year (Table 3). The 100th year value of 0.1 pCi/m* . s is about 4 times thelow-background radon flux at the research site but less than 25 % of the U.S. average of 0.43 pCi/m2 . s (NCRP1989) and about 50% of the 0.2 pCi/m2. s mean value reported by earlier studies for undisturbed,non-mineralized lands in Florida.

The indoor radon contribution due to this added radon flux was estimated using several empirically-derivedindoor radon/radon flux relationships and a baseline case of 0.2 pa/m2 . s. The PG-attributable contribution toindoor radon after 100 years of land treatment was estimated to be on the order of 0.02 to 0.19 pCi/L. Thiscontribution is small relative to the variation due to different types of land in Florida and within the uncertaintyin indoor radon measurements. When added to the 1 pCi/L or less that might be expected without PG treatmentfor undisturbed, non-mineralized land, the resulting concentration is well within the action level of 4 pCi/L.

No increases in ambient outdoor airborne radon could be detected over any of the test plots in Phase I or thefirst year of Phase II; subsequent data are still being analyzed.

Gamma Radiation. A second concern might be human exposure to external gamma radiation over PG-treatedland. Table 3 also presents the PG-attributable radiation level and the 100th-yr projection for gamma radiation.The PG-attributable gamma radiation contribution projected for the 100th year is on the order of 11% of thebackground gamma radiation levels at the experimental site. For the 100-yr land treatment scenario, themaximum external gamma radiation dose would occur to an individual who spent 24 hrs every day over thetreated land. Using the conversion of 0.001 mrem whole-body dose equivalent per µR exposure, the annualradiation dose contribution resulting from the projected PG-attributable 0.58 µR/hr exposure rate is 5.1mrem/yr. This is an upper bound -- most Florida houses are of slab-on-grade construction and, for the timespent indoors (8 or more hours per day), the indoor radiation level would be reduced because of the attenuationeffect of the concrete slab.

The projected 5.1 mrem/yr dose contribution is about 5 % of the 100 mrem/yr (above background) that isrecommended as a limit for continuous exposure by members of the general public (NCRP 1993). This is alsoconsistent with proposed Federal Radiation Protection Guidance for Exposure of the General Public thatrecommends that doses from individual sources be limited to a fraction of the limit for all sources combined(Federal Register 1994).

Radionuclides in Water. In the Phase I study (PG application at agronomic rates), PG attributable radium-226was observed in initial collections of runoff; and its presence was suggested, but not statistically significant, ingroundwater samples collected at 0.6-m (2-ft) and 1.2-m (4-ft) depths. No statistically-significant effects wereobserved among 3-yr averages. The maximum individual sample result of 1.8 pCi/L was well below the currentand proposed Maximum Contaminant Levels (MCL’s) for drinking water (Federal Register 1976, 1991).

In Phase II, statistically-significant treatment effects were observed for some, but not all, of theradionuclide-depth-collection date combinations. There was general, but not unanimous, evidence for linearity ofradionuclide concentration with treatment for the various samplings. Best estimates of PG-attributableradioactivity factors and corresponding 100th-yr projections in runoff and shallow groundwater are presented inTable 4 along with the background values observed at the experimental sites.

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Radium-226. The l00th-yr additions to concentrations of radium-226 are about four times the background valuesat the experimental site for runoff and about 120% of the background for shallow groundwater; but theprojected total values (background plus additions) are below the current, and well below the proposed, MCL’sfor radium-226 in drinking water (Table 4).

Lead-210. The projected 100th-yr additions to concentrations of lead-210 are on the order of 130 to 240% ofthe site background values. Currently there is no drinking water standard for lead-210 (a naturally-occurringbeta emitter). Since it appears that even background lead-210 concentrations in ground water approach or exceedthe 1 pCi/L concentration that corresponds to the proposed 4 mrem/yr dose limit for all beta emitters indrinking water, the entire question of lead-210 in water deserves further evaluation.

Polonium-210. The projected 100th-yr additions to concentrations of polonium-210 are comparable to (in therange of 50% of to 150% of) the site background values. The projected total concentrations resulting from the100-yr practice are 10% or less of the standard for gross alpha activity in drinking water.

Radionuclides in Forages. Concentrations of PG-attributable radionuclides in forage from treated bahiagrasspastures appear to potentially have two components -- 1) a long-term, low concentration component persistingbeyond the year of PG treatment and 2) a potential, short term, higher-concentration component that may occurin the first post-application year.4 A second observation was that whereas the other radiological parametersresponded proportionally to the PG treatment level, the radionuclide concentration in forage was “sub-linear” inresponse to PG treatment level (“saturation” effect). Hence a simple “slope” factor (pCi/g per Mg/ha) does notappear appropriate for describing radionuclide concentrations. The behavior of PG attributable radionuclides inforages is still being evaluated.

Preliminary estimates of PG-attributable radioactivity is presented in Table 5 along with the background valuesobserved at the experimental sites. Projections for the 100th yr consist of 1) the Lower Bound -- a long-term

component developed by sub-linear scaling from the 100-yr cumulative 40 Mg/ha PG addition to the soil, 2) thepotential short-term component due to the 0.4 MG/ha addition in the 100th year, and 3) the Upper Bound(long-term plus short-term components). Whereas the short-term component, when present, represents the majorcontributor to the forage radioactivity in the first year following a single treatment, it has a much lower impacton the projected activity following long-term, continuous treatment practice.

The projected PG-attributable radium-226 in the 100th year is comparable to the background at the test plots.The projected contributions to lead-210 and polonium-210 are less than the variations in the background values.These small contributions to forage radioactivity will result in only small contributions to radionuclide intake byanimals feeding on this forage, only small contributions to radionuclide content in food products of animalorigin and very small contributions to human radiation dose from ingestion of such food.

4The long-term component is presumably due to uptake from the soil and related to the radionuclideconcentration in the root zone of the soil. In the Phase II field study, a transient, elevated (five-fold)concentration was observed in the first harvest after PG treatment in one of the two sets of test plots. Thisshort-term component is presumed to be the effect of direct foliar deposition resulting in foliar uptake ofradionuclides or surface retention of PG. The reasons and mechanisms for this short-term component are stillunder investigation.

43

Table 5. Radionuclides in Bahiagrass Forage from PG-Treated Land

Radionuclide PG-Attributable Radioactivity, pCi/g Background, Mean (Std

First yr folloiving 1 Mg/ha application Projected for year 100 Dev) pCifg

Radium-226 : Lower bound (LT)a Potential STb Upper bound (LT+ST)

0.10 (0.044) 0.01 0.08

0.09 0.06 0.10 0.14

Lead-210: Lower bound (LT) Potential ST Upper bound (LT+ST)

Non-detectible 0.11 0.11

0.63 (0.395) <0.09 0.07 <0.16

Polonium-2 10: Lower bound (LT) Potential ST Upper bound (LT+ST)

0.25 (0.046) 0.01 0.05

0.08 0.05 0.09 0.10

a) LT= “long-term” or persistent component; projected from cumulative treatment practice. b) ST= “short-term” component; may or may not be present; expected only in the first yr after PG treatment.

Summary and Conclusions

Factors for PG-attributable radon flux, gamma radiation, radionuclides in water, and radionuclides in forage were developed from field experiments involving application of PC to established bahiagrass pastures at high rates (up to 20 Mg/ha or 8.9 tons/acre). Radiological values were then projected for the 100th year of a continuous practice of annual treatment at the recommended rate of 0.4 Mg/ha (0.18 tons/acre). The 100-yr projections presented here are believed to be overestimates since corrections were not made for any environmental loss.

Summary of results: 1. Radionuclides in soil - A single treatment at agronomic rates cannot be detected with current analytical

methods. The projected radionuclide concentrations added to the top 15 cm (6 in) by 100 years of annual treatment are roughly equal to the existing background at the test sites and within the range of variations seen in Florida lands without enhanced or elevated radioactivity.

2. Radon uroduction - The PG-attributable contribution to radon flux (indicative of radon originating in the soil) was projected to be about 0.1 pCi/m’ * s in the 100th year -- about 50 % of the mean for undisturbed, non-mineralized Florida lands (0.2 pCi/m2 - s). The corresponding contribution to indoor radon was estimated to be on the order of 0.02 to 0.19 pCi/L -- these values are small relative to the variation due to land type differences in Florida, are within the uncertainty in indoor radon measurements, and would result in concentrations well below the 4 pCi/L action level if added to the 1 to 2 pCi/L concentrations otherwise expected for undisturbed, non-mineralized land.

44

3.

4.

5.

6.

7.

Gamma radiation - The PG-attributable gamma radiation contribution projected for the 100th year isless than 1 µR/hr and on the order of 11% of the background gamma radiation levels at theexperimental site. This would contribute an annual whole-body dose equivalent of about 5 mrem/yr toan individual spending full time outdoors over PG-treated land. The actual annual dose contributionwould be lower for a person living in a slab-on-grade house because the radiation intensity during thetime spent indoors would be lower due to the attenuation (shielding) effect of the slab. The projected 5mrem/yr dose contribution is about 5% of the recommended limit for continuous exposure by membersof the general public (100 mrem/yr above background) and conforms with proposed federal guidancestating that doses from individual sources be limited to a fraction of the limit for all sources combined.Radium-226 in surface and around water - The projected additions after 100 years for runoff andshallow ground water are several times the background values at the experimental site. However, theprojected total values (background plus additions) are below the current, and well below the proposed,MCL’s for radium-226 in drinking water.Lead-210 in surface and ground water - The projected additions after 100 years are comparable to thesite background values. Interpretation is clouded by the fact that the background lead-210concentrations in ground water approach or exceed the 1 pCi/L concentration value that corresponds tothe proposed dose limit for all beta emitters in drinking water. The entire question of lead-210 in waterdeserves further evaluation.Polonium-210 in surface and ground water - For the 100-yr practice, the projected additions arecomparable to the site background values and the projected total concentrations are 10% or less of thestandard for gross alpha activity in drinking water.Radionuclides in forages - The projected PG-attributable radium-226 in the 100th year is comparable tothe background at the test plots. The projected contributions to lead-210 and polonium-210 arecomparable to the variations in the background values. Any human radiation dose contribution throughingestion of foods originating from animals feeding on these forages would be very small.

Conclusions. For application of Central Florida PG at agronomic rates to bahiagrass pastures:1. Additions to environmental radioactivity and radiation from limited application will be essentially

non-detectible.2. For long-term, continued (up to 100-yr) annual application of this PG at recommended agronomic rates

(0.4 Mg/ha):a) additions to the background environmental radiation and radioactivity levels would generally bewithin the range of background variation,b) contributions to indoor radon in future structures built over treated land would not be significant inlight of uncertainties in indoor radon measurement and variations expected from other causes,c) gamma radiation doses would be well within current limits,d) PG-attributable contributions to radium-226 and polonium-210 in surface and ground water would beexpected to be a fraction of the applicable drinking water standards and thus should not be of concern,ande) PG-attributable doses to humans through ingestion of animal products traceable to the treated forageshould be within the range of variation in the normal diet and, thus, negligible.One issue requiring further evaluation is that of lead-210 in water where existing background levelsmay already correspond to a significant fraction of the dose limit in proposed drinking water standards.

3.

45

References

Federal Register. Vol. 41:28402. Drinking Water Regulations. Radionuclides; 1976.

Federal Register. Vol 56, No. 138, July 18, 1991, pgs. 33050-33127. Environmental Protection Agency, 40CFR Parts 141 and 142, National Primary Drinking Water Regulation; Radionuclides; proposed rule, 1991.

Federal Register. Vol. 57, No. 107, June 3, 1992, pgs. 23305-23320. Environmental Protection Agency, 40CFR 61. National Emission Standards for Hazardous Air Pollutants; National Emission Standards for RadonEmissions from Phosphogypsum Stacks; 1992.

Federal Register. Vol 59, No. 246, Dec 23, 1994, pgs. 66414-66428. Environmental Protection Agency.Federal Radiation Protection Guidance for Exposure of the General Public,1994.

NCRP. Control of Radon in Houses. Bethesda, MD: National Council on Radiation Protection andMeasurements, NCRP Report No. 103; 1989.

NCRP. Limitation of exposure to ionizing radiation. Bethesda, MD: National Council on Radiation Protectionand Measurements, NCRP Report No. 116; 1993.

Rechcigl, J. E., I. S. Alcordo, C. E. Roessler and R. C. Littell. “Radiological aspects associated withphosphogypsum applied to an established bahiagrass pasture as a source of sulfur and calcium. ” Report toFlorida Institute of Phosphate Research by Range Cattle Research and Education Center, IFAS, University ofFlorida, Ona, FL; 1994a.

Rechcigl, J. E., I. S. Alcordo, C. E. Roessler, and R. C. Littell. “Radiological aspects associated withphosphogypsum applied to a tilled land and cropped to annual ryegrass as a source of sulfur and calcium. ”Report to Florida Institute of Phosphate Research by Range Cattle Research and Education Center, IFAS,University of Florida, Ona, FL; 1994b.

Rechcigl, J. E., I. S. Alcordo, C. E. Roessler, and R. C. Littell. “Phosphogypsum use on forages.” Fromcompendium of papers for the Phosphogypsum Fact-Finding Forum, 7 Dec 1995, Tallahassee, FL. FloridaInstitute of Phosphate Research, Bartow: 1995b.

Rechcigl, J. E., I. S. Alcordo, C. E. Roessler, and R. C. Littell. “Impact of high rates of phosphogypsum onradon emissions and on radioactivity and heavy metals in soil, groundwater, and bahiagrass forage.” Report toFlorida Institute of Phosphate Research by Range Cattle Research and Education Center, IFAS, University ofFlorida, Ona, FL; in preparation 1995b.

Roessler, C.E., J. E. Rechcigl, and I. S. Alcordo. “Phosphogypsum -- is it clean enough for agricultural use?In: Environmental radiation -- how clean is clean?“, proceedings of topical meeting, 11-14 Oct 1994,Springfield, IL. Prairie State Chapter, Health Physics Society, 90 Andover Dr., Springfield, Ill 72704;1994:6-15-6-22..

USEPA. Potential uses of phosphogypsum and associated risks. Background information document for 40 CFR61 Subpart R7 National Emission Standards for Radon Emissions from PG Stacks. EPA-402-R-92-0027, May1992.

4 6

CRITICAL DOSE AND RISK ASSESSMENT FOR USE OF WASTEPRODUCT PG IN AGRICULTURE

BY

ANTHONY C. JAMES, Ph.D.ACJ & ASSOCIATES

RICHLAND, WA

* * * * * * * *

Presenter: Anthony C. James, ACJ & Associates.

Dr. James has recently become an independent consultant after holding the position of Associate Professor in theCollege of Pharmacy at Washington State University. Prior to this Dr. James was the Chief Scientist in theOccupational and Environmental Health Protection Section of the Health Physics Department at Battelle, PacificNorthwest Laboratories. At Battelle, his primary research interest was in the development and application ofdosimetry of body tissues in humans and experimental animals, in order to address issues involved in settingpractical standards for radiological protection, and in relating cancer risks to environmental conditions ofexposure. Before joining Battelle in 1988, Dr. James had 17 years of research experience, much of it relating toradon, at the National Radiological Protection Board, Chilton, United Kingdom.

Dr. James has a B.Sc. in physics from University College in London and received the Ph.D. degree from theRoyal Free Hospital School of Medicine in London in 1969.

* * * * * * * *

Paper not available. The following is a transcription from video of Dr. James’ presentation at the Forum.

* * * * * * * *

This project was started when I was at Washington State University, with the prime contractor being BattellePacific Northwest Labs. The objective of the study was essentially to focus on the EPA’s final ruling and tolook at the science behind the dose assessments that went into the judgements that EPA made about the risks ofusing PG in different scenarios. The document that we are concerned with is the NESHAP, the NationalEmission Standards for Radon Emissions from Phosphogypsum Stacks, which as we’ve heard already, waspublished in June of 1992. There has been some response from EPA following a petition from The FertilizerInstitute which has led to relaxation in the limitation of the use of phosphogypsum in research and development.These are the people who were involved (in this study) at Battelle: John Johnson, Chief Scientist, HealthProtection Department; Richard Traub, Certified Physicist, he’s a Staff Scientist, Health Protection Dept. andup until recently, I was Associate Professor at the College of Pharmacy at Washington State University.

The scope of our study is quite narrow and focused on the critical issues that limit the potential application ofPG to agriculture and to construction. I will be talking briefly about construction after lunch. What we havedone, we are not trying to critique EPA’s exposure scenarios, although we have heard from the agronomists thatmaybe the application rates are higher than would be reasonable, certainly over long periods of time. But our

47

assessment actually takes, as the boundary conditions, the application rates that EPA has used in formulating thebackground information document. What we are setting out to do is to try to evaluate the maximum individualrisk to an individual. For example, a house that is built on a plot of land that has had an application for ahundred years, it is assumed that the individual lives for 70 years in that house in order to come up with therisk, which is an unlikely assumption, it is very much a maximum. But, we are following the methodology thatEPA uses in proximity of the occupants of the house and the inhalation of radon that seeps into the indoor air.We are not questioning or commenting on EPA’s risk factors. In fact, EPA is following the ICRP riskestimates fairly closely, in terms of, if you get a given dose per year, how much additional risk of lung canceror other cancers does that correspond to. So, we are taking the EPA’s adopted and recommended risk factors.

I would like to illustrate the approach we are taking to try and put some quantitative numbers on what ChuckRoessler was trying to extrapolate from his field observations. We are looking at a realistic, as realistic aspossible, model of the way that radon gets into a house built on a typical Florida construction, slab-on-grade.We are essentially checking out calculations that were published in 1993 by Revzan, et al. of Lawrence-Berkeley Laboratory using a different code which was developed in-house at PNL, and we are applying thesecalculation techniques to the full range of exposure scenarios that EPA has examined. What we are modeling .isnot diffusion across the concrete slab, which is the process that EPA chose to model, but rather the bulk entryof air into the building which takes into account things such things as pressure gradients. Quite often the insideof a home is a negative pressure compared to the soil gas. And that is, in fact, the mechanism that dominatessuction of soil gas into the house. The model treats various pathways by which gas can seep through cracks andfind its way past gaps between the concrete floor and the wall into the indoor air. We look at various sourceterms, for example, when you build a slab foundation, you normally introduce a backfill layer, so normally youwould excavate the native soil, which is something very relevant in the case of PG use in agriculture becausethe excavation depth is around about the tillage depth. You could reasonably claim that the surface layer fromunderneath the house itself would have been removed in the construction process. But you don’t remove thesurface layer that is contaminated with radium and additional radon from the surrounding soil around the house.So there still is a source there that leads to ingress of radon into the house. Now, that is for the radoncalculation. For the direct gamma radiation, we paid close attention to the degree of shielding that the concretelayer introduces; the degree of protection that the concrete slab introduces in reducing the dose to the occupantsof the house. EPA did not do that.

Let’s take gamma dose rates. This is an example of the rates, the calculations we come up with, compared withthe numbers that appear in the background information document from EPA. This is one scenario with a,biennial application of 1,500 lbs. of PG/acre over 100 years. The tillage mixing to a depth of 22 cm. Thecalculated increase in the radium concentration in that layer of soil is 0.6 pCi/g which is about 60% of thetypical soil concentration. So you go up from 1 pCi/g up to about 1.6 pCi/g with the addition of PG. EPAcame up with a calculation using a fairly primitive generic model, which didn’t include such things as concreteslabs, of 7.6 mrem/y. If we do the same calculation we come up with 6.0 mrem/y which is which is very closeto EPA’s model. That is assuming no floor shielding. The person is just walking around on the soil surfaceessentially. The reason for the difference is, if you look at the composition assumed by the EPA for the PGthey include too much of the thorium nuclides in relation to the radium concentration. So we’re pretty close tothe baseline calculation of the external gamma dose rate for unshielded soil. However if you add in the 10 cmthick slab you see that the dose rate you come up with is reduced by rather more than a factor of 2 from ourbaseline or about a factor of 3 from the value calculated by the EPA’s analysis. If you then assume that the 30cm of the native soil has been removed and backfilled with uncontaminated material, then you come down to amuch lower dose rate, significantly lower. Its about a factor of 60 lower than the unshielded soil.

Now let’s use the risk factors that EPA has adopted and translate those numbers into lifetime risks.EPA didn’t worry about the doses themselves, they considered the projected lifetime risks in terms of so manydeaths/10,000. And they considered that in absolute terms. They had in mind a number that was acceptableand this is an incremental number. It has nothing to do with the actual level of the background. It’s by howmuch the risks would be increased if you adopt the practice of using PG. What I have looked at here is a high

4 8

application rate, initial application this is the scenario 5 and 6, 18,000 lbs/acre, biennial application of 9,000lbs/acre. Tillage depth of 30 cm. That leads to an incremental radium concentration in the soil of 2.7 pCi/g.In other words, it multiplies the radium concentration by a factor of about 4 over a typical Florida backgroundsoil. Now to calculate incremental risks from the gamma exposure; it is 10 in 10,000. And that compares withEPA’s acceptable number in mind of 3 in 10,000 total risk. So you see this one scenario exceeded just fromthe gamma radiation component alone by about a factor of 3, EPA’s acceptable risk. Now when we repeatedthose calculations, we came up with a similar number, as I showed on the previous slide, we got about the samedose; 8 in 10,000, if you ignore the shielding provided by the floor. If you take into account the 10 cm thickconcrete shielding, then that risk drops to 3 in 10,000, which is EPA’s reference value. But you’ll notice itapplies to an extremely high application rate. If you remove the contaminated soil and replace it with importedbackfill, then the dose rate is rather more than a factor of 10 below the implied lifetime risk.

Now let’s look at the indoor radon exposure situation with the same maximum application rate. Theincremental radium concentration in the soil, as I showed you in the last slide, is 2.7 pCi/g. EPA used a verysimple diffusion model through concrete. They did the calculations for two air changes/hour (ach) which isreally too high of a ventilation rate. If they’d done the calculation for something more realistic, such as one airchange/hour (ach) they would have come up with twice the risk. The concentration of radon is roughlyinversely proportional to the ventilation rate. So the reference risk number that they came up with for thisapplication scenario, very high usage rate of biennial application 9,000 lbs/acre, is 8 in 10,000 which exceedsthe number they had in mind for acceptable risks by about a factor of 3. We’ve looked at that Revzan modeland we’ve applied it for a more realistic ventilation rate of 0.5 air changes/hour. When we did that we weregratified to find that we had pretty well predicted the average indoor air concentration of 1 pCi/L in Floridahomes taking the typical Florida soil radium content. So the model works very well and it matches typicalFlorida conditions for a ventilation rate of about 0.5 air changes/hour (ach). Now with no imported fill, inother words, if the house is built on the native soil which contains the contamination in the top surface layer, wecome up with, even though we used a different ventilation rate and a different model, we come up with a verysimilar risk estimate to EPA’s, numerically; it’s about 9 in 10,000. However, if you remove that surface layerat the time of building the house or possibly as a result of a regulation for building houses on that type of land,then the calculated lifetime risk drops below the level that EPA would consider unacceptable. In other words,the risk is acceptable in EPA’s terms.

To summarize, these calculations are by no means complete, but I think we can come to some preliminaryfindings that we expect to be evaluated at the end of the study. For the agricultural uses of the waste productPG, if you assume no side excavation and no backfill with uncontaminated material, then the EPA numbers,both the dose rates and therefore the projected lifetime risk, are too high by about a factor of 3. As for thegamma component, the radon component, EPA’s numbers are about right but they apply to a much lowerventilation rate rather than the 2 air changes/hour that they assume. If however you take what I consider amore realistic scenario with a backfill of uncontaminated material, then the maximum individual risk from PGapplication for agricultural purposes is lower than the acceptable 3 in 10,000 taking into account bothcomponents, radon and external gamma.

49

Phosphoppsum Fact-Findine Forum. Florida State Conference Center? Tallahassee, FL. December 7.1995

Scope of Doseand Risk Assessment for Agricultural Uses of Waste Product PG

ti Assume EPA’s exposure scenarios for evaluating the Maximum Individual Risk (MIR) from lifetime exposure ,in a home built on reclaimed agricultural land, i.e., after ul

0 100-y application of PG containing 26 pCi/g of 226Ra and its radioactive progeny.

ti Model the two critical exposure pathways - direct gamma irradiation - inhalation.;of radon progeny that seep into

indoor air.

ti Assume EPA’s adopted risk factors.

Phosphot yum Fact-Findin? Forum, Florida State Conference Center, Tallahassee, FL. December 7.1995

Detail of Floor and Wall for Florida Slab-on-Grade House Showing Bacli;fill

z and Native Soil

(Revzan et al., 1993)

m Concrete

Block wall

t

~~-0.45 m ------+I

PhosDhoPyesum Fact-Findine Forum. Florida State Conference Center, Tallahassee, FL, December 7.1995

from Direct Gamma Exposure.

Exposure scenario ## 5 & 6 - Initial application of 18,000 lbs/acre - Biennial application of 9,000 lbs/acre

lJl W - Tillage depth of 30 cm

- Incremental 226Ra concentration in soil is 2.7 pCi/g.

ti EPA’s calculated incremental lifetime risk is 10 in 10,000.

V’ Battelle’s calculates the following values: ,8 in 10,000 i ignoring shielding provided by floor 3 in 10,000 - with lo-cm thick concrete slab. ~3 in 100,000 - with 30-cm thick imported backfill.

gypsum Fact-Findin? Forum. Florida State Conference Center, Tallahassee, FL? December 7: 1995 Phos ho p

MIR froni Indoor Radon Exposure

d Exposure scenarios ## 5 & 6 - Initial application of 18,000 lbslacre - Biennial application of 9,000 lbs/acre

ic - Tillage depth of 30 cm - Incremental 226Ra concentration in soil is 2.7 pCi/g.

V’ EPA’s calculated incremental lifetime risk is 8 in 10,000 for 2 air changes per hour(ach).

Battelle calculates the following values for 0.5 ach: 9 in 10,000 - with no imported fill ~3 in 10,000 - with 30-cm thick imported backfill.

Phos~howtxswm Fact-Findin? Forum. Florida State Conference Center, Tallahassee. FL. December 7. 1995

Prelimi ary Findings of Battelle’s Study for ricuitural Uses of Waste Product PG

V’ Assuming no site excavation and no backfill with “uncontaminated” material, then EPA has overestimated lifetime risk from direct gamma irradiation by about a

in u1 factor of three.

With these same assumptions, EPA’s calculated incremental lifetime risk from indoor radon is about right, but for a much lower ventilation rate of 0.5 sch.

A 30-cm thick backfill with “uncontaminated” material would give an incremental lifetime MIR from PG application lower than the “acceptable” value of 3 in 10,000.

-From video, transcript of questions and answers of Agriculture Panel discussion:

POLICY PANEL QUESTIONS TO AGRICULTURE SPEAKERS

ZAMANI: (to Rechcigl) I was just wondering if, during application of the PG, while looking at the cationexchange capacity and transfer of calcium, did you look at the fate of the sodium either in California or Florida,to see if there was any ground water impact of sodium or sulphate during (PG) application?

RECHCIGL: No, we really didn’t look at sodium levels in the groundwater, though that is something we couldstill look at.

BANDY: Yes, a comment for Dr. Traxler on the economic impact, and also a question related to the use ofPG. First I work at PCS phosphate in White Springs. You said that about 200,000 tons of PG was used inpeanut farming.

TRAXLER: That is total gypsum, not phosphogypsum.

BANDY: Was your assumption that all that gypsum was switched from White Springs to central Florida? Is thatyour assumption?

TRAXLER: The assumption is not that. It’s that the threat of competition from central FL sourcing would forcethe White Springs price to fall, to meet the competition.

BANDY: OK. White Springs supplies about 60,000 tons of that total of 200,000 tons you are talking about. Wethought we used perhaps 400,000 to 500,000 tons total in Alabama, Georgia and Florida. Perhaps Dr. Sumnercould comment on that.

TRAXLER: My source of data was an IFDC publication. I can’t speak to the reliability of that number verywell. Just doing some rough calculations using our survey application rates and just assuming that gypsum isapplied only on peanuts in Georgia, it gives a reasonably close congruence with that estimate.

SUMNER: No. I don’t have any data on that at all.

YOUNG: Dr. Traxler, with regard to the economic analysis, do I understand that the rate differential wasdetermined according to the cost of transport; that you assume that the industry wouldn’t place a charge (on thePG) other that what the cost of transport was, and is that how you accounted for your differential?

TRAXLER: Yes, that would be the assumption. It’s hard to predict these future events, but one assumption thatseemed reasonable to me was that as long as the cost of offering it for use in agriculture is less than the cost ofadding it to the stacks, that is what would happen. It seems a rather conservative estimate; that they would justoffer it for free. It also seems reasonable to me, purely as an economist, that they would offer it at anything lessthan the marginal cost of dumping it on the stack and increasing the stack (volume).

YOUNG: That is really what I was trying to get. Does the economical analysis attempt to calculate thebenefits achieved through the avoided costs of having to provide that stack capacity, or not having to providethat future stack capacity?

57

TRAXLER: Yes. That is a very appropriate economic cost to include. I just have not included that yet in myown estimates.

YOUNG: So presumably it would be greater than what it is. Yet, the economic analysis reflected is really thatto the agricultural industry, but there is an additional component.

TRAXLER: Yes, precisely. That would just be the benefits of the accruing to agricultural producers and Ihave not assumed the real economic costs of maintaining and adding the stacks that are accruing to other partsof the economy. Those are things that need to be addressed in the final study.

YOUNG: (To Dr. James) In talking about the shielding factor that apparently was ignored by EPA, does thatshielding factor affect both the direct gamma as well as the indoor radiation or only one of these?

JAMES: It affects the direct gamma only.

YOUNG: What is the logic or rationale for ignoring that shielding factor, assuming that minimum housingstandards universally require flooring, probably slab flooring, but certainly some kind of flooring that wouldprovide a shielding factor.

JAMES: I don’t know, but its an obvious deficiency in the study. There is a factor of three, just there. I thinkthat the calculations were done by different people and they did not talk to each other.

GLASSMAN: (To Dr. Rechcigl) Are you aware of any cases where PG is being used currently for non-agricultural uses or non-residential uses such as highway landscaping or industrial activities?

RECHCIGL: No, that’s not my area of expertise.

OHANIAN: (To Glassman) We’ll come to that this afternoon. That is a good question.

WENZEL: (To Rechcigl and Roessler) For the two gentlemen involved with the IFAS study, from asocioeconomic standpoint, it appears to me that if we approach the Florida cattlemen and Florida Cattlemen’sAssociation with such cost savings, which are millions of dollars certainly that is an attraction for use. Haveany surveys or any anecdotal research been done in which farmers and cattlemen have been approached aboutthe cost savings for the use of PG but at the same time balancing that compared to an analysis with thepotential loss of resale if their farmland is converted on the urban edge. Especially where resale of farmlandpotentially goes to residential subdivisions.

RECHCIGL: There really have not been any surveys like that. We are just in the early stages of showingthem the benefits of using sulfur and doing some simple calculations on that. On the economic end of it, I’mcertainly not an economist but I have done some simple calculations. If it were grown for hay, and hay sellsfor $60/ton gross, the net would be $30/ton and I calculate a cost of shipping the material and actuallyspreading the material, I came up with a cost of $12/ton. This would be if we were applying two tenths of aton. There would actually be a profit of about $18/acre. That would be in a haying situation, for example.

WENZEL: Has there been any concern from the farming industry about affecting potential resale because ofprevious controversial use?

RECHCIGL: There have not been any formal surveys. During my presentation when we show the pros andcons and we show the whole picture and the results we are getting they are still very interested assuming thatthis material would be available and that EPA would condone this.

WENZEL: (To Roessler) When will we be seeing some results from the food chain studies?

58

ROESSLER: Within the next project year. It was not an issue in the EPA model and so it has not been a highpriority item, I am focusing on high priority items. We will focus on that as soon as we get some annualreports out of the way.

BANDY: (To James) In your assessment you use 18,000 lbs/acre initial application and 9,000 biennial. I am alittle confused with that versus the EPA’s use of 1,300 lbs/acre in their assessment. Could you comment onthat?

JAMES: Yes. I think I got the comma in the wrong place. It’s a numerical slip. The highest application ratewas 2,700 biennial.

ZAMANI: (To Roessler) You are in the process of doing some work on the fate of the lead-210 and theimmobilization of that within groundwater. Could you please explain this.

ROESSLER: Yes. We are collecting runoff by means of the perimeter ditches. The first year we had a dryyear and the ground absorbed all the water. The second year we were able to collect some runoff, so we havea limited amount of runoff. We collect runoff data when there is runoff. We make collections from theshallow wells. They are two and four feet deep. We analyze those samples for Lead and Lead-210, both fromcontrol plots that have not been treated and the treated plots. We will be doing some more samples in thecoming year. The field work involves that kind of sampling and the analytical work. The assessment involvestrying to compute a long term average and scaling it to unit application to get the factor and then propagating itto one hundred years. That is the extent of what we are doing. We are not doing any bench-top or any specialstudies of the fate and transport of lead-210. That is another issue in the state of Florida but that is not a partof our project.

GARRITY: I have tried to list the points on which both the speakers and the EPA have agreed and disagreed.There is more disagreement than agreement. The agreement appears to be just on the measurements of radiumin the PG from this area and the PG from Occidental, north Florida area. Disagreement seems to be oneverything else, including the total that would be used per year in applications. I am not sure anybody saidwhere the 2,700 lbs/ acre/year came from that EPA’s using. I don’t understand that. I’m not sure why, asopposed to a total prohibition, how you couldn’t come up with a series of best management practices that youcould follow, including application rates, house construction, etc. I would like some comments addressing thoseissues.

ROESSLER: My comment to the last statement is bingo.

SUMNER: The 2,700 lbs was a figure that the EPA latched onto based on a survey that was done in thefertilizer industry of use rates of gypsum throughout the country. They came up with the 2,700. You can useall sorts of caveats to limit the use of the stuff, certainly. One of the things that’s important is that northFlorida is exempt at 10 pCi/g. So you can spread 2,000 tons/acre with impunity. Yet, it’s a violation to put on1 ton of the stuff from south Florida. That’s bureaucratic bungling.

JAMES: I just want to make a correction for Dr. Bandy. Actually those numbers were correct. The highestapplication rate in the EPA document was 8,000 kg/acre. So the numbers I gave you were really the extremethat they considered. I’m sorry.

MEYER: Regarding your suggestion of looking at best management practices, California uses higher rates thanare indicated. But most of our sources are non-PG (mine sources).

PARKER-GARVIN: (To Sumner) I think my question has already been answered but I am going to ask itanyway. To what extent was regional geology taken into account in making your application rates. In thenumbers that you gave were they more uniform or average?

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SUMNER: The numbers were based on all the experimental evidence that has been conducted mainly in thesoutheast on the use of any kind of gypsum, whether it be phosphogypsum, mined gypsum or other sources ofcalcium and/or sulfur which are then all converted to a scenario of, had it been phosphogypsum. That’s whatthe rates were based on. So it’s the maximum, minimum, and most likely rates that would be applied for eachof those particular uses if the only source of material was phosphogypsum.

OHANIAN: Again I want to thank the agricultural panel for their contributions.

6 0

UTILIZATION OF PHOSPHOGYPSUM TO ENHANCE BIOLOGICAL DECOMPOSITION ANDINCREASE CAPACITY RECOVERY AT MUNICIPAL SOLID WASTES LANDFILLS

BY

CHIH-SHIN SHIEH, Ph.D.EXECUTIVE DIRECTOR

RESEARCH CENTER FOR WASTE UTILIZATIONFLORIDA INSTITUTE OF TECHNOLOGY, MELBOURNE, FLORIDA

* * * * * * * *

Author: Chih-Shin Shieh, Research Center for Waste Utilization, Florida Institute of Technology

Dr. Shieh has been conducting research for the past 10 years on developing technologies for beneficialutilization of waste materials in both marine and terrestrial environments. He has published about 20 scientificpapers in the field of waste management and has served as session chairman at several national and internationalconferences.

Dr. Shieh received his Ph.D. degree from the Florida Institute of Technology and his Master’s degree from theState University of New York at Stony Brook.

* * * * * * * *

Introduction

A two-year study is currently being carried out to develop a methodology to use phosphogypsum as covermaterial in landfills to enhance biological decomposition of municipal solid waste (MSW) and at the same timereduce the accumulation of phosphogypsum and the volume of cover material remaining in a MSW landfill. Thestudy is being undertaken by the Research Center for Waste Utilization at Florida Institute of Technology inMelbourne, Florida, under the sponsorship of the Florida Institute of Phosphate Research (FIPR). The studymeets the guidelines for approaches (2) and (3) in the FIPR’s 1993 Research Priority Report to achieveObjective #1 of Priority #1 “Phosphogypsum and Phosphogypsum Pond Water”.

Biodegradation of MSW is a microbiological process. Wastes containing substantial amounts of fermentableorganic components can be treated biologically under anaerobic conditions. Under anaerobic conditions, sulfatecan be used by bacteria to replace oxygen as energy source that is needed during biodegradation process.Phosphogypsum, which contains more than 70% of sulfate, could be used as an alternative oxygen source formicroorganisms to conduct anaerobic biodegradation of MSW in landfills.

Project Objectives

The overall goal of the study is to demonstrate that phosphogypsum can be used as an oxygen source forsulfate-reducing bacteria, and hence, enhance the decomposition of MSW in landfills. Studies in year 1 wereconducted to determine the extent that phosphogypsum can be used to enhance biodegradation processes forMSW in landfills and to investigate the methodology for the application of phosphogypsum in landfills. Studiesin year 2 are to develop optimum conditions and a standard procedure that can be practically used for a landfilloperation. The successful completion of this study will help Florida minimize the problems of managing bothphosphogypsum and municipal solid waste.

6 1

Research Approach

To obtain meaningful results on biodegradation of the waste within a short period of time, grass clippings andwood mulch were used as the waste matrix in the study. A series of studies were carried out to define reactionconditions for biodegradation using phosphogypsum. The approach to the study initially was to develop ananaerobic biodegradation system (ABS) that allows a study to simulate landfill conditions. The waste matrix wasthen prepared for exposure to designated conditions. By-products of biodegradation were continuously monitoredthroughout the period of the study. At the end of each exposure the residual waste matrix was recovered andthen was determined for the reduction in total biodegradable solid (TBS), which was then used to assess thedegree of biodegradation.

The following tasks are being conducted to achieve the goal of the study.Task I: Development of An Anaerobic Biodegradation SystemTask II: Determination of Applicability of Using Phosphogypsum for Anaerobic BiodegradationTask III: Development of Optimum Conditions

l determination of phosphogypsum/MSW ratiol application as final cover or operational cover (layers)l determination of thickness and number of layers

Task IV: Evaluation of FeasibilityTask V: Development of a Practical Procedure and Formation of Recommendations

Primary Findings

As a result of a series of operational testing, an effective equipment configuration for the biodegradation ofstimulated landfill materials involving application of phosphogypsum was developed. The anaerobicbiodegradation system, in general, consists of the lysimeter, gas monitoring system, temperature control system,and leachate collection system.

The experimental results showed that the use of freshly clipped grass and mulch as the waste matrix providedneeded information on anaerobic biodegradation within a certain period of time. The results also showed thatlysimeters actively produced gases, indicating that the digestion system developed in the study was suitable forconducting anaerobic digestion of waste material.

For the purpose of the study a hypothesis was developed suggesting that, by introducing phosphogypsum to aanaerobic digestor, the production of CO2 would be prolonged and the formation of CH, would be delayed. Thenet outcome would be an additional degradation of organic matter during the stage of sulfate reduction. Data ongas composition collected from the study support the hypothesis.

Results on the reduction in total biodegradable solid (TBS) of the waste matrix showed that, when less than 40%of phosphogypsum was mixed thoroughly with the waste at different phosphogypsum/waste ratio, higher percentreduction in TBS was found for the lysimeter containing higher contents of gypsum indicating that use ofphosphogypsum provided a favorable condition for anaerobic biodegradation, and hence, enhanced thebiodegradation under anoxic conditions.

Assessment of Feasibility

Based on the laboratory results, an effort is being made to assess the engineering, environmental, and economicfeasibility of using phosphogypsum to enhance biodegradation of MSW in landfills. Technically, application ofphosphogypsum in landfills is an engineering and environmentally sound approach since no special equipmentwould be needed and no release of leachate from the lined site would occur. Economically, use ofphosphogypsum in landfills would save cost on daily cover material, space and cost for piling up

62

phosphogypsum on the existing sites. The transportation cost, however, would reduce the economic value ofusing phosphogypsum in landfill application. Detailed analyses of the feasibility assessment will be orallypresented and discussed at the forum.

Recommendations

Though the ongoing laboratory study has revealed that, using phosphogypsum in landfill application is anengineering, environmentally, and economically sound approach in managing phosphogypsum, furtherinformation is needed to determine the function of phosphogypsum on enhancing microbiological activities inlandfills under natural environment. Therefore, a field study is needed to demonstrate laboratory findings. Thefield study shall further determine the method of application, e.g., mixing phosphogypsum with the waste orusing phosphogypsum as daily or final cover.

63

SULFUR RECOVERY FROM PHOSPHOGYPSUM

BY

TIMOTHY J. KENDRONKEMWorks TECHNOLOGY, INC.

MULBERRY, FL

* * * * * * * *

Author: Timothy Kendron, KEMWorks Technology, Inc.

Mr. Kendron has been KEMWorks vice president since 1995 and has more than 25 years of technical andmanagement experience involving various aspects of engineering. He has specialized in the thermal processingof solid materials and various wastes such as phosphogypsum, municipal waste, coal and biomass. He has co-authored several papers with FIPR Research Director G.M. Lloyd describing the recovery of sulfur fromphosphogypsum and given presentations at conferences around the world on processing solid wastes.

Mr. Kendron is a graduate of the Illinois Institute of Technology with a Bachelor’s degree in MechanicalEngineering and a graduate of the Management Development Program at Georgia State University.

********

Introduction

Sulfur value recovery from phosphogypsum (typically as sulfuric acid) has always been of interest to the wetprocess phosphoric acid industry. Its implementation would close the sulfur loop and help isolate phosphoricacid economics from periodic sulfur price increases. Sulfuric acid was produced from natural calcium sulfate inGermany prior to World War II. In South Africa, a similar process has operated since 1972 usingphosphogypsum as the sole raw material to produce 300 tons per day of sulfuric acid. Newer plants have beenbuilt and operated in China. The typical drawbacks of the conventional, installed technologies are: highinvestment and production costs, high energy consumption, environmental problems and by-productmarketability problems. Advanced technologies targeting these problems have been explored. The FloridaInstitute of Phosphate Research (FIPR) has been instrumental in the development of an innovative technologyincorporating sintering on a circular grate as the main processing step. The process produces sulfuric acid and asolid by-product suitable for road construction primarily from phosphogypsum. This process was developed inconjunction with the Davy McKee Corporation with major support from Freeport McMoRan. In thispresentation, this technology is referred to as the FIPR Process.

FIPR Process Background

The FIPR Process incorporates processing equipment widely used in the iron and steel industry for sintering oflarge quantities of solids. This equipment is designed to thermally react phosphogypsum, waste pyrites, wasteclays and a low cost carbon source for the production sulfuric acid and aggregate for road construction. Patentprotection for this process has been assigned to FIPR The process development began in 1985 and hasprogressed through the construction and operation of a process test plant in Louisiana. The test plant

65

demonstrated that the main technical goals of the process were achievable on a relatively large-scale. The plantconsumed 35 tons per day of phosphogypsum to produce about 25 tons of aggregate and 30 tons of sulfuric acidper day. Other work following completion of the demo plant test program has been completed to furtheranalyze, improve and refine this process.

As with any process technology, it is necessary to consider optimization steps to keep the process up-to-date andin-line with new enhancement possibilities. One example of such improvements with advanced process testingand development can be seen with work completed at FIPR a few years ago. A brief series of phosphogypsumsintering tests incorporating a new enhancement technique were completed with FIPR’s assistance. The primarygoal of the tests was to evaluate thermal processing improvements that could be achieved by introduction of lowfrequency sound (infrasound) into reaction systems such as the FIPR Process. The infrasound technique hadbeen successfully demonstrated in other process and combustion applications.

The tests confirmed that reaction rates could be significantly increased with the introduction of the lowfrequency sound into the reaction zones. The Figure 1 indicates the reductions in equipment sizes which couldbe expected. The section on economics evaluates the impact of this aspect of process improvements.

This type of evaluation for process optimization is important and would be impractical today due to the limitedamounts of phosphogypsum available for use.

Leaching and Radioactivity Concerns

The positive impacts of the FIPR Process on certain characteristics of concern associated with phosphogypsumis very significant. The typical definitions used in most published descriptions and almost all media sources isthat “phosphogypsum is a solid waste generated by the phosphate industry that contains traces of heavy metalsand is slightly radioactive.”

The heavy metals contained in a typical aggregate sample from the FIPR Process are shown in Figure 2. Themetals leaching (metals removal from the solid by acidic liquid) characteristics for two common testingprocedures is given. As you can see the metals are “locked” in the material resulting in leachates well belowEPA leaching standards.

66

Figure 1

Figure 2

FIPR Process Aggregate Leachate Analysis

Element

AS

Ba

Cd

Cr

Pb

&

Hg

Se

EP Toxicity TCLP EPA Leachate Standards (Wl) W&/l) &k/l)

1.6 0.882 5.0

0.52 0.17 100.0

0.01 0.01 1.0

0.01 0.05 5.0

0.05 0.1 5.0

0.01 0.05 5.0

0.001 0.005 0.2

0.01 0.1 1.0

The radiation assay measurements in raw phosphogypsum and the FIPR Process aggregate are presented in Figure 3. After the material is processed to remove sulfur in this process, the remaining solid residue (proposed aggregate) is significantly lower in available radon and gamma radiation. The increased concentration of radium is expected as the process acts to reduce total amount of solid materials but encapsulates any radium present. The important fact is that the emissions produced by the remaining radium are lower and in the key area of concern; radon emanation. The processed solid is nearly 27 times lower in radon gas release than that emitted by stacked phosphogypsum.

Figure 3

Radiation Assay Measurements Phosphogypsum and Aggregate

Material

Phosphogypsum

Aggregate

Radium 226 Wikm)

29

51

Available Radon (PCibQ

3.50

0.13

Gamma (pRem/h)

30

20

68

Process Economics

The technical viability of removal of sulfur from gypsum is well demonstrated. The significant improvementsand production of a salable by-product as offered by the FIPR Process have been confirmed at a large-scaledemonstration facility. The process economics when evaluated by “standard” methods have continued todiscourage the commercialization of the recovery of sulfur from phosphogypsum.

When evaluated in the late 1980s, the FIPR Process was economically breakeven with a price of sulfur at about$135/ton, assuming an aggregate value of $5/ton. This was based on a detailed analysis prepared by SRIInternational of Menlo Park, CA. This assumed a cost penalty for supplying phosphogypsum to the plant; $1/tonof phosphogypsum, a carbon source price of $55/ton and a power cost of $50/MW and $2.50/MMBtu naturalgas.

Recent Economic Factors

There have been some recent developments that have an impact on these economics. Some of thesedevelopments and their cost implications are particularly important for the FIPR Process when evaluated forcentral Florida locations. The following highlights some of these developments:

l Aggregate value

Aggregate for road construction is actually being imported from foreign countries into the Gulf Coast area. Thedemand for high quality aggregate for road construction in the Gulf Coast region and particularly Floridapresents a strong potential market. Current value of these aggregates in central Florida is $4.50 to $7/ton.Vulcan Materials with central offices in Birmingham, AL has opened a large quarry in Mexico producing roadconstruction materials. Large quantities of aggregates from this operation are being barged to the Port of Tampaand delivered to Florida markets. There have been rejections of at least a portion of these materials for use infriction courses (highest value material $6 - $10/ ton) in Florida. Phosphogypsum aggregate as produced in theFIPR Process was evaluated as acceptable for friction courses. If the Florida Department of Transportationprojections are realized over the next 10 to 15 years, demand for high quality aggregates in Florida will be veryhigh.

The Strategic Highway Research Program sponsored by the U.S. Department of Transportation recentlyreleased findings indicating that the real area of concern for improved asphaltic concrete highways is the qualityand specifications of the so-called filler materials; aggregates, sand etc. not the liquid asphalts. Theimplementation of specifications for more suitable aggregates needed for the proposed “Super Pave” highwaysystem for North America could open even more valuable markets for the FIPR aggregate.

l Real costs of phosphogypsum storage in new, lined stacks

Some companies which stack phosgyp have implemented lined storage systems. This results in a cost of about$1.50 - $2 /ton of stored waste. This does not include containment and treatment of runoff from rainfall orcontrol of seepage from the stack. Also, stack closure costs are not included in this number but must beconsidered when stacking continues. Independent surveys and evaluations have indicated that an “all-in-cost” forproper phosphogypsum storage approaches $5/ton.

Rather than penalize the process economics, I suggest that a credit be given for the consumption ofphosphogypsum by avoiding higher stacking costs.

l Relatively low energy and carbon source prices

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The costs for natural gas and avoided costs for electric power production have remained fairly stable. Thecarbon source required for the FIPR process could be obtained from a new process recently put into commercialoperation by SGI of La Jolla, CA. The process produces a low cost, low-volatile solid fuel and various liquidfuels from high sulfur, inexpensive coal. A circular grate system is the coal processing reactor. This solid fuelcould be used to reduce raw material costs for the FIPR Process.

The availability of this material and continued low cost for natural gas would reduce the capital cost andoperating expenses particularly when considering replacement of electricity generated by existing sulfuric acidplant power generation installations.

. Improved FIPR reactor design

The sintering, circular grate reactor is the single most expensive equipment item in the capital requirement for acommercial-scale plant using the FIPR Process. Taking advantage of the reduction of reactor size predicted bythe infrasound tests previously discussed, the estimated cost for the entire battery limits plant would be reducedby about 4 % .

Updated FIPR Process Economics

By applying these factors to the previously presented base economics, the FIPR Process could be consideredbreakeven with $105/ton sulfur for a plant producing 920,000 tons/year of sulfuric acid from about 1.2 milliontons of phosphogypsum. This represents a reduction in product cost of about 21% when compared to the earliereconomics. Asummary of these factors and impacts on the process economics are included in Figures 4 and 5.

Even with the relatively low price of sulfur currently in place in Florida, the alternative of recycling sulfurvalues from phosphogypsum may be closing the economic gap.

Figure 5

Sulfuric Acid Production Cost Comparison - F’IPR Process

SRI International PEP Review 86-2-2 1988 920,000 tons/year of Sulfuric Acid

Cost Category Sulfuric Acid Production Cost

-1988

Modified Sulfuric Acid Cost - 1996

Source of Impact

Investment - BL $MM U.S.

All Raw Materials and Utilities

70

$2456/tori H,SO,

67

$18.59/tori H,SO,

Increased Grate Factor

Lower Carbon Source/Utilities Cost Gypsum Costs

$5 .OO/ton

---------------------

$26.84/tori H,SO,

$8.00/tori

--------------_-------

$18.02/tori H,SO,

Increase in value of high quality aggregate

-----------------____

Includes All Variable and Fixed Costs

Other Costs $17.71/tori H,SO, $17.29/tori H,SO, Plant Overhead, Taxes and Insurance, Depreciation

---------------------

$4455/tori

----------------------

$35.31/tori

__-__________________

21% reduction in net cost

71

Need for Access to Phosphogypsum

The restriction for removal of phosphogypsum from stacks for the various proposed uses has severely limitedthe development of advanced utilization techniques. This prohibition also essentially guarantees future additionsto the already extensive inventory of this waste. The knowledge that the raw material would essentially beunavailable even if a “breakthrough technology” were developed is extremely restrictive to any interest ineffective, alternative utilization of stacked phosphogypsum.

Summary

Phosphogypsum is a technically and environmentally suitable source for sulfur to an industry currentlyconsuming large quantities of this raw material. The FIPR Process has demonstrated some attractive advantagesover older technologies particularly in markets needing large quantities of high grade road constructionmaterials. The environmental advantages of reducing rates of phosphogypsum stacking from the long termperspective are extremely important.

The economics have historically placed sulfur recovery from phosphogypsum at a disadvantage when comparedto simply purchasing sulfur. The new developments discussed here may be closing the “sulfur value” gap.

In order to take advantage of these developments and any other promising technologies, phosphogypsumshould be available as a raw material for the production of both sulfuric acid and other valuable by-products.The environmental concerns associated with stacking phosphogypsum can be significantly lessened only byimplementation of environmentally responsible methods of utilization.

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PHOSPHOGYPSUM AND ARTIFICIAL REEFS:AN ARTIFICIAL REEF MANAGEMENT PERSPECTIVE

BY

RONALD R. LUKENSGULF STATES MARINE FISHERIES COMMISSION

********

Author: Ronald Lukens, Gulf States Marine Fisheries Commission.

Mr. Lukens has been the Assistant Director of the Marine Fisheries Commission since 1987, developinginterjurisdictional policies and programs and coordinating an interstate technical subcommittee on artificial reefdevelopment and management. He has been involved with assessing and monitoring artificial reefs since 1975and has published seven papers on the topic.

Mr. Lukens has a Master’s degree in Marine Biology.

**********

It has been said that one man’s trash is another man’s treasure. It is simply good business to convert whatwould ordinarily be considered a waste material into a useful and valuable commodity. This, however, must bedone under careful scrutiny that assures the public that the proposed use of a waste material is beneficial,non-hazardous, and is not being proposed merely as a way to get rid of waste burden, particularly as it relatesto impacts on the environment. Is phosphogypsum a treasure? Is it an opportunity? While the answer to thesequestions will depend upon the application and gathering a great deal of technical data, I would like to frame thequestions in the context of artificial reef applications and the kinds of issues that concern artificial reef programmanagers.

Artificial reef development in the United States began in earnest in the late 1960s and 1970s. Early efforts wereaccomplished by volunteer groups who were primarily interested in improving recreational fishing opportunities,a situation which continues. Throughout this history of development, “materials of opportunity” have been usedto build reefs. What are materials of opportunity? Loosely defined, they are largely man-made materials whichhave outlived the useful life for the purpose for which they were originally intended. Examples include oil andgas structures, ships and other vessels, automobile bodies, tires, concrete rubble, among a long list of others.This reliance on materials of opportunity has been at once both beneficial and burdensome to artificial reefmanagers; beneficial in that they are usually readily available and cheap to obtain, and burdensome becausewaste managers view artificial reefs as a good way to dispose of their “product” while benefiting theenvironment. I classify the last as burdensome, because not all waste materials can be considered compatible foruse as artificial reef material, and because political pressures from local governments, industries, and others canbe brought to bear to force the use of materials that may otherwise not be desirable by an artificial reefprogram.

73

Standards and Criteria

The following are categories for criteria and standards for artificial reef materials as established in the NationalArtificial Reef Plan (Stone 1985):

a. function in providing habitat for marine organisms,b. compatibility with the marine environment,c. durability and stability in the marine environment, andd. availability

These are the areas which are considered by an artificial reef manager when determining whether or not amaterial will be used.

There are a number of examples of materials of opportunity that have been used that can help illustrate theseconcerns. Many years ago, automobile tires, a significant waste disposal problem, were used experimentally asartificial reef material. From a practical standpoint there are a number of benefits and drawbacks to usingautomobile tires; however, once it was widely known that tires could be used in this context, pressure wasbrought to bear on artificial reef programs to use tires as a means of reducing the waste burden on localgovernments. As a result, a number of problems have arisen, not the least of which is tires being deposited onbeaches after storms and ending up in shrimp fishermen’s nets. Today we know that there are some very basicengineering principles that can be applied to using tires in this context to make them more suitable. Related tothe standards and criteria, the function of tires as beneficial marine habitat is still being debated, and can best becharacterized as applicable on a case-by-case basis. Tires are basically compatible with ‘the marine environment,because they do not break down very easily. Tires are unstable in water unless significantly ballasted. Finally,tires are readily available but labor intensive to use. Currently, use of tires as artificial reef material has nearlyceased.

Another good example is the need to find a suitable use or disposal mechanism for the ash residue fromcombustion of coal for energy production. This ash material can be combined with portland cement and createdesigned structures for use as artificial reef material. There has been pressure on artificial reef programs forseveral years to use this material; however, until relatively recently there were no general guidelines foranalyzing the ash for marine applications, nor for mixing the material to produce a chemically stable structurewith adequate compressive strength to withstand the rigors of the marine environment. Recently, a set of generalguidelines were adopted for the Gulf of Mexico region for use of coal fly ash, which is only one of the wastestreams resulting from coal combustion. Related to the standards and guidelines, structures can be built fromaggregate mixtures using coal fly ash that will provide habitat for marine organisms. The compatibility questionrelated to the potentially toxic components in coal fly ash required much research and testing before guidelinesfor its use could be developed. Structures constructed from coal fly ash and cement mixtures are durable andstable, and the material is readily available.

Research

Research must be conducted that clearly determines whether or not phosphogypsum is a biological orenvironmental threat when used in artificial reef or other marine applications. In the case of coal fly ash, the ash

resulting from the combustion of coal from different geographic sources resulted in ash that has differentchemical compositions. Testing must be done on ash proposed for use in the marine environment to determine iscomposition. If this is the case with phosphogypsum, the range of chemical composition of the material fromdifferent sources must be determined and related back to that source. If materials in phosphogypsum are knownto be toxic to living organisms, then it must be determined if such substances are chemically bound in themixing process, or if they are physically bound. In the case of coal fly ash, it was determined that toxiccomponents were chemically bound, such that if a block of ash and concrete were pulverized, no trace of thetoxic chemicals could be detected. If the toxic components are physically bound, there is a concern related to

7 4

releasing the material if the phosphogypsum/concrete structure deteriorates over time. There is also concernabout potential bioaccumulation in marine organisms if such toxics are made available.

Protocols must be developed for testing the chemical composition of phosphogypsum, and for determining ifdifferences exist in the chemical composition of the material from different sources. Protocols must also bedeveloped for mixing the material to provide the compressive strength necessary to assure durability over time.These protocols must be published and made available to the public.

State Artificial Reef Programs

A recent survey of marine fishery management agencies revealed that artificial reef programs within thoseagencies have a relatively low priority. This, of course, varies from agency to agency; however, the obviousresult of this conclusion is that funding available to conduct artificial reef activities is always limited and seldomflexible. There are personnel, equipment, and funding constraints on almost all coastal artificial reef programsin existence. This situation, as you might guess, affects much of what the programs can accomplish in any givenyear. The various sources of funding needs include staffing and overhead, cost of materials, cost of preparationof materials for deployment, at sea deployment operations, biological and physical monitoring of artificial reefs,among others. Materials that are inexpensive to obtain, readily compatible with the marine environment, andrelatively easy to deploy are very attractive to artificial reef managers. Materials that must be purchased, arelabor intensive to prepare for deployment, must undergo processing to assure environmental compatibility, andare difficult and expensive to deploy are typically avoided.

Assuming that research and testing determine that phosphogypsum can be used safely in the marineenvironment, it is my belief that the following things must be in place if the material is to be successfully usedin the context of artificial reefs or other marine applications.

. the material cannot be considered a commodity, but must be made available at no cost.

. fabrication of artificial reef structures or units can be costly and labor intensive. This cost should beborne by the industry, unless arranged otherwise with individual programs.

. delivery of phosphogypsum or structures to construction and staging sites can be difficult for artificialreef programs with limited resources. The industry should work out arrangements for delivery withindividual programs.

. deployment and other at-sea activities related to using phosphogypsum can be expensive and labor andequipment intensive. Arrangements must be made to provide the artificial reef programs with theequipment and expertise needed to conduct such at-sea activities.

. The demand, on an annual basis, for artificial reef materials that must be purchased by artificial reefprograms is very low in comparison to the amount of phosphogypsum that is available, especially inlight of the availability of coal fly ash for this use.

. The availability of a quantity of waste material cannot be the driving force behind the type of materialsused by an artificial reef program. Artificial reef managers must have the freedom to select thosematerials that satisfy the standards and guidelines established, while at the same time can be usedwithin the programmatic limitations of funding, manpower, time, and equipment availability.

While it is true that in general artificial reef programs do not enjoy a high priority within the state marineresource agency’s fisheries programs, they all enjoy a great deal of public support and encouragement. Theprimary reason for this is that the creation of a new artificial reef automatically creates new opportunities foranglers to catch fish and divers to enjoy diving activities. Artificial reef program managers are sensitive to this

75

public support and are concerned with anything that may erode that support. One of the concerns is the publicperception of using “questionable” materials as artificial reef material. This concern was of major importanceduring the development of the guidelines for using coal fly ash. This concern must be addressed ifphosphogypsum is to be used by state artificial reef programs.

Finally, one promising marine application of phosphogypsum/cement aggregate is the enhancement of oysterbeds through the development of a cultch material on which oysters can settle. Historically, clam and oystershell have been used as oyster cultch; however, clam shells are no longer available due to political andenvironmental issues associated with dredging of the shell, and oyster shells are economically difficult toreclaim from oyster processing plants for cultch. Typically, oyster fishery programs must replenish cultch forsettlement of oysters on a regular basis to replace the material taken during the harvesting process. This couldprove to be a steady market for application of phosphogypsum; however, there are a number of relatedconcerns, including

. competition with coal fly ash, which is being proposed for this use,

. potential to pulverize the cultch material by using tongs and dredges to harvest oysters

. sedentary nature of oysters related to potential for bioaccumulation of the chemical components ofphosphogypsum

. related public health implications

. public perception related to the use of a byproduct as cultch and its impact on the already burdenedoyster industry

Conclusions

I believe that the phosphate industry has a great deal of work to do if natural resource managers are to beconvinced that phosphogypsum can be used safely and effectively as artificial reef material and oyster cultch inthe Gulf of Mexico. Assuming that the industry is interested in pursuing marine applications of the material, aclose working relationship with the marine resource management agencies, and in particular the artificial reefprogram managers, must be established. We should all proceed with a positive attitude toward finding value inbyproducts that result from the various industries that serve the American public and contribute to our quality oflife. But, we must proceed cautiously with a sincere concern for the long-term protection of this space ship wecall Earth.

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PRELIMINARY EVALUATION OF THE USE OF PHOSPHOGYPSUM FOR REEFSUBSTRATE IN THE GULF OF MEXICO REGION

BY

CHARLES A. WILSONLOUISIANA STATE UNIVERSITY

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Author: Charles Wilson, Louisiana State University - Department of Oceanography and Coastal Sciences.

Mr. Wilson, currently professor and chairman of the above department at LSU, began his oceanographic careerworking on shrimp trawlers and charter fishing boats off the coasts of South Carolina and Florida. Afterteaching at the University of South Carolina, he joined the faculty at LSU and worked to develop the LouisianaArtificial Reef program in conjunction with the Department of Wildlife and Fisheries. He has publishedextensively in fields of marine biology, shrimp mariculture and offshore reef effectiveness.

Dr. Wilson received his Bachelor’s degree from Hampton Sydney College and the Master’s and Doctoraldegrees in Marine Fisheries from the University of South Carolina.

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Phosphogypsum (PG), a solid by-product of phosphoric acid production, has been classified as a“Technologically Enhanced Natural Radioactive Material” because it contains radionuclides and some tracemetals in concentrations which may pose a potential hazard to human health and the environment. The maindisposal method, onsite stockpiling, has resulted in at least 33 PG stacks (average area of 224 acres per stack)located in all Gulf States except Alabama and has created a tremendous management problem. Environmentalconcerns associated with PG disposal, coupled with increasing land costs for stockpiles, has promoted researchon alternative beneficial uses of this solid waste that will result in applications considered protective of publichealth.

A sound alternative to present disposal practices must address the issue of airborne radioactive contact with thepublic, while providing evidence that PG reuse or recycling is more economical than the long term cost ofdisposal. This issue has prompted states including Louisiana, Florida and Texas to investigate alternatives forthe utilization of this material. Commercial utilization is the best long term, economical solution to reducingcurrent and future PG inventories. Four broad categories for alternative uses of phosphogypsum have beenidentified: 1) agriculture, 2) building construction, 3) road construction, and 4) other applications includingartificial reefs, riprap, retaining wall back-fill, coastal erosion barriers, and jetty stone. In addition to the abovementioned coastal applications, the use of PG as an artificial substrate for oyster settlement has been suggestedto complement the declining supply of natural oyster shell substrate in the Gulf region.

The utilization of phosphogypsum for underwater applications provides the best means for minimizing publicexposure because the airborne vector of transmission is eliminated or, at least, significantly diminished. Mostother alternatives, while proposing economic solutions to the growing phosphogypsum inventories (agriculture,roadbed aggregate, building material, etc.) do not address the fundamental issue. That is, the high potential forhuman exposure to radium and its decay products (principally radon). An initial uncontrolled pilot demonstration

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study and a follow up two year study conducted at Louisiana State University showed that PG/cement testblocks placed in the Gulf of Mexico supported a diverse population of surface attached and burrowingorganisms, indicating the potential of using PG for offshore artificial reefs.

In addition to radionuclides, PG contains some trace elements in concentrations which EPA believes may pose apotential hazard to human health and the environment. The EPA has identified a number of potentialconstituents in PG from some facilities that could, under the appropriate conditions, cause adverse health effectsor the restriction of potential uses of nearby surface or groundwater resources. Elements identified includearsenic, lead, cadmium, chromium, fluoride, zinc, antimony, and copper. Among these elements, onlychromium and arsenic were identified in PG from some facilities at concentrations that may pose significanthealth risks.

There has been some research related to the leachability of toxic substances from PG stacks. To date nosignificant leaching of trace elements (copper, nickel) from nine phosphogypsum stacks located in Florida. Moreimportantly, all core samples contained toxic element concentrations lower than the EPA definition of toxicity,with the exception of arsenic. In the case of arsenic, analyses indicated the metal could not be leached thus,would not be available to impact the environment. In our studies leaching tests performed on compressedPG/sand-cement blocks (70%/30%) we found that all elements measured (Cd Pb Cr and As) were below EPAdrinking water quality standards. In fact, Pb and Cr leachate was higher from sand-cement controls than the PGcomposites.

In a similar study on artificial reefs of coal ash, it was found that toxic elements might diffuse at an extremelyslow rate. Various short-term assays and longer exposure experiments made in the laboratory and open sea inthe same study showed no evidence of uptake or concentration to toxic levels. However, a few of their testsindicated an inhibition of biological functions at very high concentrations of leachates, or of suspended coal ashparticulates. Therefore, it was recommended that more investigations should be conducted to better determineand clarify potential infiuences of reef building materials in marine environment. Research on cement stabilizedcoal ash has now progressed to large scale demonstration projects with positive results.

Both Florida and Louisiana have a need for low-profile material for use in their inshore reef programs.Louisiana also needs suitable substrate material for maintaining suitable oyster habitat. The economic value ofthe fisheries associated with these needs is significant. In 1986 it was estimated that the recreational fishery ofLouisiana spent over 200 million dollars (not including multipliers). The Louisiana oyster industry is valued atover $40,000,000 per year. Most of this fishing activity occurs in the shallow, inshore and near shore coastalwaters.

In a preliminary offshore trial that involved the investigators, PG-cement and sand-cement control blocks wereattached to oil rigs and the blocks were inspected for fouling organisms after 60 days. For blocks that remainedintact, no differences in the densities of amphipods, barnacles and total organisms were found. Most impressivewere the number of attached animals present on the control and test blocks. Amphipods are important foodsources for many fish, and were found in abundances of 4000 - 6000 per 4” diameter x 4” height cylindricalblocks. The artificial reef phenomenon partly results from increases in diversity and quantity of food, andphosphogypsum blocks appear to develop fouling communities that are similar in diversity and abundance to thesand-cement control blocks.

Phosphogypsum stabilized with cement should provide suitable substrate for oyster sediment based on itschemical constituents. In the process of settling, oyster larvae key in on hard substrate as a settling substrate.This life history strategy assures that oyster larvae will settle in areas where other oysters are present. Althoughit has been shown that oyster larvae will settle on other materials, oyster larvae will preferentially select outareas where calcium is present. Phosphogypsum (calcium sulphate) provides a chemically suitable substrate forthe settlement of oyster larvae. However, it is necessary to thoroughly investigate the effect of associatedcontaminates that are mixed in with calcium sulphate on oysters as they grow.

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To investigate the possibility of accumulation of radium226 and selected heavy metals over time when organismsare cultured in the presence of PG, we designed an aquarium experiment consisting of four componentsrepresenting different levels of an aquatic food chain: algae (Chaetoceros muelleri), copepods (Harpacticusobscurus), grass shrimp (Palaemonetes sp.), and gulf killifish (Fundlus grandis). Cultured algae were providedto copepod mass culture systems to which unconsolidated PG was added on a regular basis. The PG culturedcopepods were subsequently fed to grass shrimp which were held in a three aquarium array. Three 70% :30%(PG:cement) blocks were placed in each of these aquaria to provide an environmental exposure to PG. Aftertwo weeks of feeding on the PG cultured copepods, the grass shrimp were fed to aquarium-held gulf killifish atan average rate of one shrimp per fish per day. Each of the three killifish aquaria were also provided with six70% :30% (PG:cement) blocks to maximize contact opportunity. The killifish were maintained in this manner forthree time periods (45, 90, and 135 days) before being removed for analysis. Controls were provided by gulfkillifish which were fed grass shrimp cultured with commercial shrimp pellets as their food source. Both thecontrol grass shrimp and the control killifish aquaria were also furnished with 70%:30% (sand:cement) blocks.Control killifish were also harvested at 45, 90, and 135 day intervals for analysis.

Whole body nitric acid digests of the experimental (N = 14), control (N = 13), and wild caught (N= 10) killifishwere analyzed to determine the constituent concentrations of seven elements: radium226, copper, zinc, cadmium,lead, chromium, and arsenic. In comparisons of their concentrations with the concentrations found in thewild-caught specimens, only copper (1.5 times higher in experimental fish) and cadmium (8 times higher inexperimental fish) showed any statistically significant differences in mean concentrations between theexperimental and control groups. The tissue level of cadmium in killifish was 0.058 ppm. Mean concentrationsfor equivalent exposure times between the experimental and control groups showed statistically significantdifferences for cadmium, lead, chromium, and arsenic. However, these results are difficult to interpret as bothgroups evidenced maximum mean concentrations at 90 days exposure which were subsequently reduced at 135days exposure.

The next step in our investigation employed four one-quarter acre ponds located at the Louisiana Department ofWildlife and Fisheries Marine Laboratory located on Grand Terre Island, Louisiana. Two of the ponds wereseeded with 600 four inch by two inch cement consolidated PG cylinders (70% :30%, PG:cement) arranged insix equidistantly spaced “reefs” of 100 cylinders each. The two remaining ponds were similarly seeded withcylinders of cement consolidated sand of like proportions. A ten horsepower submersible pump was used todeliver ambient seawater to the ponds in a flow through manner. All four ponds were allowed to becomenaturally stocked with eggs and larvae of a variety of marine organisms. At the end of one year, the ponds weredrained and seined to harvest the macrofauna of each and the blocks were removed for assessment of oystergrowth.

A total of three species of macroinvertebrates (oyster, white shrimp, and blue crab) and 15 species of fisheswere collected from the four ponds. Representative individuals from each species found in each pond werefrozen for future elemental analyses. Mean numbers of species (and biomass) for the two experimental pondsand the two control ponds were 10.5 (32.35 kg) and 14 (32.41 kg), respectively. The mean number of speciesin the control ponds, however, was inflated by five species which were represented by single individuals. Bluecrab were abundant (and quite large) in all four ponds; the fish species silver perch, spotted seatrout, and spotwere also particularly abundant in all. Statistical comparisons of the distributions of proportional speciesabundances and proportional species biomasses among ponds revealed all four ponds to be quite dissimilar. OnlyPond 1 (control) and Pond 4 (experimental) showed similar distributions of species abundances and all pondsshowed unique distributions of biomasses among species. The two ponds seeded with PG blocks weresubjectively judged by the authors to be suffered no ill affects from their presence.

Oyster growth was evident and abundant on both the PG:cement and the sand:cement blocks; all exposed blocksurfaces were blanketed with a dense growth of these organisms. In many cases the oysters had formed a crownon the top of the blocks which measured 6-8 inches in diameter. Again, no evident differences in oyster growthwere noted between the experimental and control ponds.

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The ultimate decision for using PG as colonizing substrate for oysters, reef material, or other aquatic applicationwill depend upon completing this line of research and active dialogue with regulatory agencies. Results to datewarrant continued pursuit of lab trials and field testing of the ecological safety of PG towards this goal.

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THE MERSEBERG PROCESS--A PARTIAL SOLUTION TO THE PHOSPHOGYPSUM PROBLEM?A POSITION PAPER

WILLIAM C. BURNETTENVIRONMENTAL RADIOACTIVITY MEASUREMENT FACILITY

DEPARTMENT OF OCEANOGRAPHYFLORIDA STATE UNIVERSITY

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Author: William Burnett, Florida State University.

Dr. Burnett joined Florida State University in 1977 after a postdoctoral appointment to the State University ofNew York at Stony Brook and a short-term position as a visiting scientist at a Federal University in Brazil. Heis currently a Professor of Oceanography and Director at FSU and Director of the Environmental RadioactivityMeasurement facility, which is a research program emphasizing the application of natural U/Th series nuclidesto address problems in the earth, marine and environmental sciences. Current research also includesdevelopment of improved techniques for measuring artificial, as well as natural, radioactivity in theenvironment. Dr. Burnett holds concurrent appointments as a guest lecturer with the training department ofCanberra Industries, Inc. in Meriden, CT and as a technical advisor for Environmental Physics, Inc. inCharleston, SC.

Dr. Burnett earned a Ph.D. from the University of Hawaii in 1974.

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The Problem

Florida has 600-700 million metric tons of phosphogypsum in storage on 27 stacks with another 30 million tonsbeing added each year. The U.S. Environmental Protection Agency (EPA) has ruled that phosphogypsum mustbe placed on stacks or mine cuts and that only gypsum containing less than 370 Bq . kg-’ (10 pCi . g-l) 226Ra canbe removed for agricultural purposes. The EPA regulates the distribution and fate of this by-product principallybecause of its radium content and its potential for generating the gaseous radioactive daughter, 222Rn. This is animportant consideration as the main use of gypsum in the United States is for construction of wall board or“sheetrock” used in houses. The stacks themselves, however, are a serious problem. Besides the obvious wasteof a potentially valuable by-product and the unsightly physical appearance of the stockpiles, the main problemassociated with phosphogypsum storage is the potential effect on the surrounding environment, especially thewater resources in the vicinity of gypsum stacks. Can anything be done about this wasteful and potentiallyenviromnentally-damaging situation?

Some Ideas

Many previous suggestions have been made for phosphogypsum use including: (1) use for construction of roadbeds; (2) recovery of elemental sulfur either chemically or microbially; (3) direct agricultural application as afertilizer; and (4) use of phosphogypsum blocks for construction of artificial reefs. At present, there does notappear to be a high degree of confidence that any of these approaches will be successful in terms of large-scale

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volume reduction. Can large-scale radiochemical purification be done economically? Perhaps, especially ifcombined with a process that will also result in an economically-attractive product.

The Merseberg Process

One possibility for such a process is the conversion of phosphogypsum to the two end products (calciumcarbonate and ammonium sulfate) of the so-called “Merseberg” ammonocarbonation reaction. One of theseproducts, ammonium sulfate, is an excellent fertilizer that adds both sulfur and nitrogen to the soil. The otherreaction product, calcium carbonate, could be used for neutralizing acidic process waters associated with thephosphate industry, used as an additive for cement, or calcined to drive off the CO, which could be recycled forthe production of the ammonium carbonate needed in the Merseberg process. Chemically, this procedure maybe represented by the following reaction:

CaSO, * 2H2O + (NH,),CO, ------ w (NHJ2S04 + CaCO3 + 2H,Odihydrate ammonium ammonium calciumgypsum carbonate sulfate carbonate

This method is now used on a commercial scale with waste phosphogypsum in India, China, and Indonesia.Furthermore, a FIPR-sponsored study conducted recently in my laboratory at Florida State Universityinvestigated the flow of radionuclides through the entire process. The results showed that while concentrationsof uranium and radioactive daughter products varied in the phosphate rock samples (and thus in the resultingphosphogypsum) from these overseas plants, the radionuclides which originally concentrated in thephosphogypsum all reported to the by-product calcium carbonate. The resulting ammonium sulfate is thus verylow in radium and other radionuclides, lower than found in most natural materials.

Need For Ammonium Sulfate

The expanding role of sulfur in accelerating crop production, especially in tropical countries, has become morewidely recognized in the last few years. Sulfur is an essential nutrient for plants and it contributes to increasedcrop yields both by providing a direct nutritive value and by improving the efficiency with which plants useother essential nutrients, especially nitrogen and phosphorus.

During the last two decades, changes in agricultural practices and fertilizer manufacture have had a majorimpact on sulfur availability. “Green Revolution” technology, with corresponding increases in crop yields andmultiple cropping, will continue to increase demands for sulfur. The aggregate sulfur availability to agriculturalsoils, on the other hand, has been declining over the last several years for 3 reasons: (1) many countries neverhad any policy of supplying sulfur to soil (although it was applied inadvertently via the use of fertilizer that alsocontained sulfur); (2) the fertilizer industries have been replacing sulfur-containing fertilizers (such asammonium sulfate) with sulfur-free fertilizers (as urea) because of high distribution costs and the perception thatsulfur itself was of little importance; and (3) the environmental concern for cleaner air has reduced the supply ofsulfur via “acid rain” from the atmosphere.

Thus, we are now facing a serious “sulfur gap” in many areas. Although sulfur deficiencies in soil are notalways easy to recognize, there is a growing body of evidence that the lack of sulfur is often responsible forlower productivity. In general, the situation is that while higher crop yields require more sulfur, the actual trendis of a decreasing sulfur supply as a result of lower levels of inadvertent addition and atmospheric pollution.Consequently, sulfur deficiency problems in soils are now becoming widespread.

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Economic Considerations

We thus have an interesting situation where, it appears, that two problems could be resolved by the samesolution. We need more ammonium sulfate to fill the “sulfur gap” and we have a lot of waste gypsum inFlorida. Furthermore, it has been demonstrated that one can produce good quality, radionuclide-free ammoniumsulfate from phosphogypsum by the Merseberg reaction. So, what’s the big deal? -- Let’s get started!Unfortunately, it isn’t that simple.

One of the principal reasons that the Merseberg process can be economically realized in India and some otherAsian countries is because sulfur is in short supply there and has to be imported. The availability of by-productgypsum, therefore, provides an inexpensive raw material for producing a sulfur-containing fertilizer. Incountries with plentiful supplies of sulfur resources, the principal economic problems lie with the relatively lownitrogen content of ammonium sulfate and the availability of ammonium sulfate from other sources. Since(NH,),SO, contains only 21% N while urea contains 46% N, the production and subsequent transport costs perunit nitrogen is obviously higher for ammonium sulfate. Fertilizer manufacturers have thus tended to favor theso-called “high analysis” fertilizers (note that “high analysis” here refers to content of nitrogen or phosphorus,not sulfur). In spite of this apparent cost disadvantage, the prospect of being able to provide sulfur as well asnitrogen to soil to overcome the sulfur deficiency problems referred to earlier and to address the problem ofphosphogypsum disposal in the phosphate industry has great practical appeal.

Commercial-scale production of ammonium sulfate has not been considered economically feasible in Floridabecause the price has been kept low due to the by-product production of ammonium sulfate from otherindustries. Most ammonium sulfate today is a co-product from the manufacture of the nylon intermediate,caprolactum. The U.S., now the leading ammonium sulfate producer, accounts for 75 % of its product viacaprolactum. However, new technologies have developed recently which have lowered the amount ofammonium sulfate to product ratio from 5:1 to about 1.3:1. In addition, BASF is said to be developing amethod for recycling carpets for nylon that wouldn’t produce any ammonium sulfate at all. Thus, the demandfor ammonium sulfate has been improving over the last few years as the sulfur requirements are recognized andthe main supply via caprolactum production may diminish substantially. These trends have produced a relativelysteady increase in the world ammonium sulfate prices over the last three to four years. The situation isimproving.

Synopsis

The current phosphogypsum situation in Florida is unfortunate, as the practice of stockpiling is unattractive frommany points of view. Not only are the gypsum stacks unsightly and present a possible environmental problem,but they will require long-term expenditures for maintenance and monitoring. A “pass-through” technology,which would convert the waste product to a useful commodity is clearly a more efficient use of our resources.

Although the economics of large-scale ammonocarbonation of phosphogypsum remain uncertain, I suggest thatthe following points make the Merseberg process potentially attractive: (1) fully-developed fertilizerinfrastructures are already in place in Florida; (2) the gypsum is readily available; (3) the need for sulfur willdrive the demand for ammonium sulfate while supplies from other industries are diminishing; (4) thestoichiometry of the ammonocarbonation process is such that about 30% more gypsum is consumed thanammonium sulfate produced -- waste minimization is thus achieved; (5) significant amounts of the by-productCaCO, could also be used by the phosphate industry; and (6) the significant construction and maintenance costsassociated with gypsum stacks, estimated to be in excess of several million dollars per year, could be reducedand eventually eliminated. Furthermore, now that the State of Florida has decided to “close” inactive andunlined gypsum stacks within the next several years, there are new costs to consider. Although the costestimates vary widely depending upon the size of the stack and other variables, an average closure cost of ~ $20

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million per stack is realistic. It is also important to note that these cost estimates do not include the on-goingcosts of environmental monitoring. Is this really how we want to solve our problems?

A Suggestion

I suggest that it seems appropriate at this stage to review our strategies in terms of dealing with this waste.Additional research should be encouraged to find a cost-effective means to reprocess phosphogypsum.Conversion to a useful product, even without a significant profit margin, should be preferable to the hugeexpense and endless monitoring required for environmental isolation.

Closing stacks is not only an expensive proposition, it is following a very pessimistic route. After spending afew tens of millions of dollars on the closure process and performing the required decades of environmentalmonitoring, “new” uses for phosphogypsum would be of little interest. Why not give Florida’s environmentalscientists, chemists, engineers, and radiochemists an opportunity to develop a viable scheme to purify or convertphosphogypsum into environmental safe and commercially useful products. Lets take the optimistic course andencourage research to find answers. If only l0-20% of the cost of closing a single stack were devoted toresearch on this specific problem, there is an excellent chance that better solutions could be found. Creativeideas are needed to solve thorny problems.

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PHOSPHOGYPSUM UTILIZATION AS A CHEMICAL RAW MATERIAL

BY EDWARD J.A. O’HANRAHAN & LAWRENCE W. NISBET, JR.

GALLOWAY CHEMICAL DIVISIONO’HANRAHAN CONSULTANTS, INC.

CLEARWATER, FL

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Presenter: Edward J.A. O’Hanrahan, Galloway Chemical Division.

Mr. O’Hanrahan is President and Chief Chemist of Galloway Chemical Division, a 35-year-old company thatO’Hanrahan Consultants, Inc. acquired in 1980. Mr. O’Hanrahan has been instrumental in developing the firstlow pressure drop catalyst composite unit used in an automotive emission control device and has many otherjoint patents involving heat transfer machinery for the chemical and food industries. His current interest inputting phosphogypsum to use as a chemical raw material source.

Mr. O’Hanrahan has a Bachelor’s degree in Chemistry from Dublin University in Dublin, Ireland.

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Phosphogypsum is a man-made source of several valuable raw materials. It is the purpose of this paper tooutline the recovery of a few of these elements, and to show the potential value of three of them.

SULPHUR: From sulphuric acid (H,SO,) to Calcium Sulphate (CaSO,) - phosphogypsum - to HydrogenSulphide (H,S) through a Claus Unit to Sulphuric Acid.. . seems like a perpetual motion machine. It is in thechemical world, Sulphur is a cost item, a raw material.

CALCIUM SULPHIDE: Resulting from the reduction of calcium sulphate with carbon (C) in the temperaturerange, 850 to 1,000 degrees centigrade.

CaSO, + 2C = CaS + 2C0,easy to write, but difficult to do

My corporation has funded research on this process at a dollar expenditure of six figures. We have learned thatour investment was not enough to start the commercial production of CaS.

CaS has to be manufactured under strictly controlled conditions to produce a product of 90% purity or better.

Moisture will cause CaS to release H,S prematurely; oxygen will lower the, percentage of CaS recovered.

Technical research has shown that with ideal temperature control, an inert nitrogen blanket, accurate feedcontrol and a constant RPM of the kiln.. .gram quantities of calcium sulphide (of 90 % or better purity) can beprepared from phosphogypsum. Our objective is to make CaS, not in gram, but in tonnage quantities on acontinuous basis.

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We believe that using the controlled conditions above and a controlled cooling regimen, we can manufactureCaS in large quantities. Further work will require commercial scale equipment at an estimated investment costof three million dollars.

Calcium sulphide (55%) has an f.o.b. market value of $500/ton in moisture-tight packages. Current tonnageavailable worldwide is less than 500 tons. However, an estimated 100,000 tons of CaS will be required withinfive years to treat and remediate heavy metal contaminated soils.

Pro-Forma

Assumptions:Volume: 12,000 tons the first year, with growth to 50,000 tons by year five.

Revenue: $500/ton

SalesLess: coal cost

phosphogypsumlabor costsfixed capital cost

$6,000,000600,000 (15,000 tons @ $40)

250,000 (25,000 tons @ $10)150,000300,000 ($3 million amortized over 10 years)

Gross margin $4,700,000

Payout: Less than one year

CaS has a special usage in the hazardous waste management of sites contaminated with heavy metals (copper,chromium, lead, arsenic, et al.) After reacting these soils with calcium sulphide, they meet or exceed the TCLPStandards of the EPA, and in particular, the California standards.

At this cost per ton, the remediation industry would use more. The U.S. EPA favors the use of the dry powderover the related compound, a liquid 29% active calcium polysulphide. Calcium polysulphide readily releasesH,S into the environment during its reaction with metals in the contaminated soils. CaS powder treatmentreleases much less H,S and charcoal filters are able to control those H,S emissions.

RADIUM: Treatment of the CaS in a wet cycle generates the hydrosulphides of calcium and the small quantityof radium present in the phosphogypsum. The silica contamination in the gypsum can be filtered off anddiscarded. The solution containing the soluble radium can be treated in an enclosed ion exchange system torecover the radium for use by the nuclear medicine industry.

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AN EXTENDED MORTALITY FOLLOW-UP STUDY OFFLORIDA PHOSPHATE INDUSTRY WORKERS

FINAL REPORT

HARVEY CHECKOWAY, Ph.D.1

NICHOLAS J. HEYER, Ph.D.1

PAUL A. DEMERS, Ph. D.2

1UNIVERSITY OF WASHINGTONDEPARTMENT OF ENVIRONMENTAL HEALTH

SEATTLE, WASHINGTON

2UNIVERSITY OF BRITISH COLUMBIAOCCUPATIONAL HYGIENE PROGRAMME

VANCOUVER, BRITISH COLUMBIACANADA

JUNE 1995

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Note: Dr. Heyer was unable to attend the Forum due to other commitments.

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Executive Summary

This report presents findings from an updated cohort study of workers in the Flonda phosphate industry. Theoriginal study was performed in the early 1980s by a research team from the Occupational Health Studies Groupat the University of North Carolina (UNC). This updated study was conducted by researchers at the Universityof Washington, Department of Environmental Health. Both the original and updated studies were sponsored bythe Florida Phosphate Council, and Dr. Harvey Checkoway was Principal Investigator in each instance.

The original study was prompted by reports in the late 1970s of lung cancer clusters among industry employees.Ionizing radiation from phosphate ore sources was of particular interest in this regard. A further motivatingfactor for the UNC study ‘were reports by the Environmental Protection Agency of elevated indoor radon levelsin homes built on land that had been reclaimed subsequent to phosphate mining.

The UNC study traced the mortality experience, during 1949-78, of approximately 23,000 male workersemployed for a minimum of 12 months cumulative service in the Florida operations of the 15 then membercompanies of the Florida Phosphate Council. Cohort membership further required that workers had beenemployed for at least 3 months continuous service in the industry between 1949 and 1978. The original analysiswas restricted to male workers. The most noteworthy results form the UNC study were small excesses of lungcancer mortality in both white and non-white male workers compared to U.S. white males. However, therewere no lung cancer excesses when the workers’ death rates were compared to Florida state mortality rates.Analyses were next performed to identify work areas and specific agents that may have been associated with

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disease excesses within the industry. The study revealed no evidence of causal associations with specific agents,including ionizing radiation, dust, and acid mists.

Two other mortality studies among Florida phosphate industry workers were conducted, respectively, byresearchers from the National Institute for Occupational Safety and Health and Johns Hopkins University.Neither study revealed any clear exposure/disease associations for lung cancer, although the Johns Hopkinsstudy findings were suggestive of an elevated lung cancer risk in workers employed in shipping and drying jobswhere radiation and dust exposures were assumed to be highest. The present study was an update of theoriginal UNC study. The same cohort of male workers from the UNC study was included in our update. In theupdate, we examined the cohort’s mortality patterns during the years 1949-92, thus adding 14 years of follow-upto the UNC study. In addition, separate analyses were performed and are presented for female workers. Theprincipal focus of our update was lung cancer. The goals of the study were: 1) to determine whether phosphateindustry workers have experienced increased risks from lung cancer and other diseases compared to national,state, and local county rates; 2) to determine whether there have been lung cancer hazards concentrated invarious work areas or jobs; and 3) to examine associations between lung cancer and exposures to specificchemical and physical agents. The agents considered were: total dust, silica, sulfuric and phosphoric acid mists,fluorides, ammonia, alpha radiation, gamma radiation, and elemental phosphorus.

The cohort included 18,446 white male, 4,546 non-white male, 1,523 white female, and 306 non-white femaleworkers. The median duration of follow-up for the race/gender groups ranged from 17 to 23 years. Vital statusas of the end date of the study, December 31, 1992, was ascertained for 98 percent of male workers, and 96percent of female workers. Death certificates indicating cause of death were obtained for 95 percent ofidentified decedents.

The first set of analyses compared mortality rates, by cause of death, between the cohort and the national, state,and local county rates. Standardized mortality ratios (SMR) were computed to estimate relative excesses anddeficits of mortality in the cohort. An SMR of 1.0 indicates that mortality in the cohort was identical to that inthe comparison population (e.g., national population), whereas an SMR greater than 1 .0 indicates a relativeexcess in the cohort, and an SMR less than 1.0 reveals a relative deficit in the cohort. Among white males, totalmortality was nearly identical (SMR=0.99) to that of the U.S. white male population during the same timeperiod, 1949-92. A small excess of lung cancer was observed for white male workers compared to U.S.(SMR=1.19) and Florida state (SMR= 1.12) rates; however, compared to local county rates there was no overalllung cancer excess (SMR=0.98). Non-white males experienced a deficit of all causes mortality combinedcompared to U.S. rates (SMR =0.80). There was a small excess of lung cancer in non-white males relative toU.S. rates (SMR=1.13), but no elevations compared to either state (SMR=0.95) or county rates (SMR=0.94).White females had lower than expected mortality for all causes (SMR =0.80), and lung cancer (SMR=0.80)when national rate comparisons were made. Similar lung cancer deficits were found for white female workersrelative to state and county rates. The small numbers of total deaths (22) and from lung cancer (1) in non-whitefemales precluded a meaningful interpretation of their mortality data. Mortality from diseases other than lungcancer was largely unremarkable in all race/gender worker groups.

On the whole, the mortality patterns of the workforce did not demonstrate excessive risks. The findings fornon-white males were typical of the healthy worker effect, which is characterized by a lower all causes mortalityrate in workers compared to national and regional populations. Selection for adequate health to gain andmaintain employment is the principal reason for the healthy worker effect. White males did not experience ahealthy worker effect, in regard to all causes and cardiovascular disease mortality, as would be anticipated. Wehave no explanation for the apparent differential healthy worker effect by race among males.

The detailed analyses that followed focused on lung cancer among male workers because lung cancer was ofgreatest prior interest. These analyses were limited to males because there were very small numbers of femaleworkers in production jobs. We conducted a series of mortality rate comparisons among subgroups of the

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wolkers in which lung cancer risk was related first to employment duration in any of 23 job groupings definedaccording to process type, and second with respect to cumulative exposure to chemical and physical agents (totaldust, silica, sulfuric and phosphoric acid mists, fluorides, ammonia, alpha radiation, and gamma radiation). Theclassification of exposures was not based on actual worker exposure levels because such data were sparse or inmany instances missing. Instead, a qualitative exposure rating scale was devised in consultation withknowledgeable industry personnel. The cumulative index for each of the chemical and physical agents took intoaccount exposure level differences between jobs and over time. Process changes and improvements in industrialengineering were reflected in the exposure rankings. A worker’s cumulative exposure value for a particularagent (e.g., silica) thus represents the product of the duration of his exposure to the agent and the relativeexposure intensity for that agent for each job held. Exposures occurring within the preceding 15 years were notincluded in these analyses under the assumption that 15 years is the average latency period for lung cancer.

There were no consistent associations observed between lung cancer mortality and employment duration in anyof the 23 process groupings of jobs. The results for cumulative exposure to specific agents revealed only modestor irregular risk gradients. The most noteworthy findings were slightly increasing lung cancer risk trends withcumulative exposure to both alpha and gamma radiation among white males, but no associations with radiationin non-white male workers. Two other agents, silica and acid mists, had been linked etiologically with lungcancer in some previous studies of other industries, but we did not detect consistent or strong associations in thisstudy.

The findings from this study are in general agreement with those of the original UNC study. There continue tobe only small overall lung cancer excesses in males compared to national rates. Mortality rates from otherdiseases were usually less than national averages, which is consistent with a healthy worker effect selectionphenomenon. Exploration of potentially causative relations with work in particular job types, or in relation toexposures to various chemical and physical agents, did not suggest evidence of a clear work-related hazard forlung cancer.

A possible association of lung cancer and ionizing radiation has heen of concern to the industry since the late1970s. The observed trends of lung cancer risk with alpha and gamma radiation were not prominent and wereseen only among whites. The absence of consistent relations between radiation and lung cancer in non-whiteworkers weakens arguments of cause-and-effect. We did not find any strong associations with exposures to otheragents, especially silica and acid mists which were of a priori interest. Our conclusions concerning lung cancerare that this disease has not occurred excessively throughout the industry, and that there are no identifiableoccupational exposures that have created consistently elevated risks among segments of the workforce.

One important limitation of this study is that there was insufficient workplace exposure data spanning past timeperiods to enable a true quantitative assessment of exposure/disease associations. The net effect of thisdeficiency, which occurs quite commonly in occupational epidemiology studies, is that some true associationsmay be missed or, more likely, understated because of exposure classification errors. It is doubtful that we havefailed to identify or have seriously underestimated important associations of phosphate industry exposures withlung cancer.

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-From video, transcript of questions and answers of Other Uses Panel discussion:

POLICY PANEL QUESTIONS TO OTHER USES SPEAKERS

OHANIAN: The papers for this morning’s presentation are on the table. There should be enough copies foreveryone but if there is not, leave your name and we’ll get it to you by mail. I also have to apologize andmake a correction. We do have an EPA representative here from the Atlanta office, Paul Wagner. He is fromthe EPA radiation Atlanta office. The next panel is on several other uses of PG. The two people who couldn’tbe with us today, one of whom is Dr. Zeller, it turns out that he went to Bosnia. He is working onconstructing housing using PG as a base. Also Nicholas Heyer from the University of Washington was unableto be with us this morning. We have his paper and if time allows our Executive Director, Dr. McFarlin, willgive a brief summary of the paper.

COLEMAN: (To Kendron) You commented on the aggregates as having anti-skid qualities. Would you tellme who did that testing?

KENDRON: I received most of the figures from a company called Macasphalt which is located in WinterHaven.

GLASSMAN: (To Wilson) Was any follow-up research done on Cadmium levels that were found as far ashealth risks in the toadfish?

WILSON: No those were very recent results and we have not followed them up at all. We still have anothersix or seven months left on the project so we will address that.

GARRITY: (To Shieh) In your process did you notice any production of odors from using Calcium Sulfatebecause I know that when we have disposals of sheetrock in construction demolition debris landfills and othertypes of landfills, that kind of problem does arise. I was wondering if you noticed anything like that.

SHIEH: Yes. The process generates hydrogen sulfide. I think that is where the odor comes from. We expectthat this is also an indication of the coolness??? of the process. Hydrogen sulfide production has been aconcern. However, right now we have an approach to solve that problem. In landfill operation they use aflaming or flaring system to bum off hydrogen sulfide. Also, new technology is coming up that will converthydrogen sulfide using a solar system. The Solar Energy Center has come up with a device which will do that.So with future technology, I think that the production of hydrogen sulfide could be beneficial to the sulfurproduction. Also an area of research, the hydrogen sulfide could react with the metal components in themunicipal solid waste to form the metal sulfide precipitation. Without precipitation some trace metals that arean environmetal concern could be also precipitated out from the leachate. So that area requires some furtherinvestigation. We are not able to do it now.

GARRITY: This is a question submitted from the audience. It is addressed to Dr. Burnett. You mentionedtrying to get some additional funds for research. The question is posed that if we were able to arrive at someagreeable way to permit more extensive use of phosphogypsum, would there be ways for the money saved bythe industry to be used to fund research such as you’re talking about. So I guess that the question goes beyondjust yourself.

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BURNETT: I think that question raises an interesting point. I think it is better answered by someone from thephosphate industry because I don’t really know. My understanding is that with the current rule from DEP thatthe closure is going to be paid for by the industry. Those costs are obviously passed on to the consumer. It’s aninteresting point and I would definitely support it. The main point I was trying to make was that I think thatresearch is an optimistic way of looking at a problem because you don’t get involved with research unless youthink your going to find a solution. My feeling is that there are solutions. You’ve heard some very creativeideas today. With a concerted effort, even short term 3 to 5 years, with that kind of funding basis, I think youcould come up with some things that have not even been thought of.

YOUNG: (To Shieh) You suggest that your work is now ready for field investigation. Do you in fact intend toproceed with field investigation .? Do the current rules even allow a field investigation? Are you going to beusing a municipal land fill and do you need a test site?

SHIEH: From the research viewpoint, I hope that I can carry on a field study but right now the EPA has alimitation in terms of the quantity of PG that can be used so that issue needs to be addressed. If the EPAcannot lift that limitation, even though we have very positive levels that the results show that this would be agood approach, then further studies may not even be a question. If this is a research project, the EPA mayallow us to use more PG for the purpose of the study.

COLEMAN: Dr. Wilson, I had several questions from the audience. I think one will basically sum it up.What were the results of comparing the meiofauna and shrimp treated and control populations with respect tocadmium and other substances?

WILSON: That analysis is being done right now. We just harvested the pond two months ago and we don’thave any heavy metal data from the organisms that were reared in the two ponds yet, or the tanks, that’s beingdone right now. Except for the fish.

COLEMAN: There was a follow-up question and that is, are we to understand that only a two week period waschosen for shrimp feeding?

WILSON: Yes.

COLEMAN: Are you sure that’s long enough?

WILSON: No. By no means. This was our first shot at doing it and in a bioaccumulation study that is a verygood question, ‘how long do you run an experiment like that?’ We certainly like to raise the shrimp from hatchall the way up to harvest size, or a size at which they would be consumed, and that would be a follow-up study.But this was our first pass at doing it with very limited funds.

OHANIAN: We would like to thank the other uses panel. Thank you very much.

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DESIGN, CONSTRUCTION AND EVALUATIONOF EXPERIMENTAL STABILIZED GYPSUM ROADBASES

BY

DR. DONALD SAYLAK, P.E.RESEARCH ENGINEER; TEXAS TRANSPORTATION INSTITUTE

TEXAS A&M UNIVERSITYCOLLEGE STATION, TEXAS

Author: Donald Saylak, Texas A&M University.

Dr. Saylak joined the Materials Science Division of the Civil Engineering Department at Texas A&MUniversity in 1972. He holds a joint appointment with the Texas Transportation Institute and is the Director ofthe By-Products Utilization and Recycling Research Center. Prior to this, he was Head of the EnginineeringMechanics Laboratory at Thiokol Chemical Corporation and Chief of the Mechanical Behavior Section at theAir Force Rocker Propulsion Laboratory. His research activities have included pavement materials developmentand testing, recycling, experimental mechanics, fracture and age-life prediction of polymeric materials. He hasnumerous publications in each of these areas. He served as Chairman of the Joint Army-Navy-NASA-Air ForceWorking Group on Mechanical Behavior of Solid Propellant, was named AIAA Outstanding Contributor of theYear (1969) and received the Air Force Systems Command Award for Distinguished Research and Development(1970).

Dr Saylak holds a bachelor’s degree from the University of Pittsburgh, a master’s degree from the University ofDelaware and the Ph.D. from Texas A&M University.

* * * * * * * *

Introduction

Rising costs associated with assuring high quality construction and maintenance of highway systems is spurringthe continued development of more cost effective construction methods and materials. Waste and “pollution”by-product gypsums from coal-burning power plants, hydrofluoric acid, and phosphoric acid productionindustries are currently being given considerable attention in Texas, Louisiana, Florida and other states.

A number of researchers (1, 2, 3, 4, 5) have provided evidence that by-product gypsum can be used as aroadbase or subbase material through stabilization with either portland cement, fly ash or combinations of both.When properly mixed, compacted and cured, these materials will develop sufficient strength for fieldapplications. Both laboratory and field results show that gypsum, when sufficiently stabilized and compactedshould qualify for most roadbase and subbase applications.

Roadbases for city streets, shopping centers, truck terminals, parking lots and loading platforms have beensuccessfully constructed in the Houston area of Texas using cement and fly ash-stabilized Phosphogypsum andFluorogypsum. Personal contacts with two suppliers; Gulf States Materials (Fluorogypsum) (6) and MobilChemical Compay near Pasadena, Texas (Phosphogypsum) have revealed a better-than 95 percent success rate

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on over 700 projects (7). TTI was involved in the mix design development of the base courses utilizing both ofthese by-product gypsums (8, 9, 10). The use of Phosphogypsum has been discontinued due to concernsresulting from excessive radon and heavy metal concentrations in this by-product.

Problem Areas with By-Product Gypsum Roadbase Construction

It is when attempts were made to extend the stabilized-gypsum roadbase concept to state and federal roads thatconstruction difficulties have been encountered. One project using a ten percent cement-stabilizedphosphogypsum base on Texas SH 146 proved unsuccessful (11). Two other projects in Texas (5) usingvarying amounts of fly ash and cement as stabilizers also had to be replaced after less than a year in service. Invirtually every case, when construction difficulties were encountered, the problems could be related to one ormore of the following sources:

a. Excessive moisture added during construction.b. Over stabilization.c. Incomplete mixing.d. Incompatible stabilizers, prime coats, etc.e. Insufficient compaction and weather scaling.f. Road opened to traffic too soon.

a. Moisture: Overwatering in the field, either while trying to achieve a specified moisture content or tomaintain dust control, will weaken the base during its most critical period of strength development.One of the prime locations for this type of damage is at transitions from one day’s work to the next.An improperly prepared transition at the end of a roadway or when changing from one mix design toanother are also potentially vulnerable to swelling due to the accumulation of excessive moisture orimproper compaction.

b. Stabilization: Different states qualify their allowable strengths for stabilized bases based on differentnumbers of days permitted for curing. For example, Texas requires 650 psi strength after seven days,whereas Illinois specifies 650 psi after fourteen days. Strengths above 350 psi are considered sufficientfor light to medium traffic loads. Strengths from 550 to 650 psi are required for medium to heavytraffic loading. The chemical interaction between gypsum and cement is one which proceeds at a slowrate of hydration. The rate is further affected by the need to use slower curing sulfate resistantcements. As a consequence, the inability to reach a required seven-day strength is usually compensatedby adding excessive stabilizer.

c. Mixing: Blending of mix ingredients can be accomplished successfully either in-place (2) or in a pugmill (5). The latter has advantages of allowing for field calibration checks to ensure compliance withjob mix specifications, and achieving good mix homogeneity. Smaller projects, or projects whichcannot be conveniently located near a pug mill, may favor mixing in-place. In any case, the ability todeliver good mix homogeneity is imperative. Experience with one project in Texas indicated that thelower two inches of an 8-inch base constructed by mixing in-place was not successfully blended by thepulverizer (5). This problem could have been alleviated by constructing the section in multiple lifts orusing a pulverizer with longer tines. Unfortunately, these deficiencies are not normally encountereduntil core samples are taken usually long after the road has been opened to traffic.

d. Incompatible Stabilizers and Prime Coats: Cement type and content have a great influence onstrength development in stabilized byproduct gypsum mixtures. Tricalcium aluminate (C,A) is one ofthe principal aluminate compounds in portland cement. To achieve sulfate resistance in portlandcement concretes ASTM C150 recommends that the C,A content in Type II cements should be kept

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below seven percent. Studies involving cement-stabilization of gypsum-based mixtures have shown thatC,A contents no greater than 4 percent should be used to prevent sulfate attack and swelling (1, 5).The hydration of C,A in portland cement involves a reaction with sulfate ions which are supplied by thedissolution of gypsum. The primary initial reaction is:

C,A + 3CSH, + 26H ---------t C,A&H,, (Ettringite)

Ettringite is a stable hydration product only while there is an ample supply of sulfate available. If allthe sulfate is consumed before the C,A has completely hydrated, the Ettringite transforms to amonosulfoaluminate (MSA) which contains less sulfate.

2C,A + C,AS,H,, +4H ---------> 3C,ASH,,(MSA)

When monosulfoaluminate is brought into contact with a new source of sulfate ions, Ettringite isreformed.

C,ASH,, + 2CSH, + 16H ---------> C,AS,H,,

This potential for reforming Ettringite is the basis for sulfate attack of portland cements when exposedto an external supply of sulfate ions. Once Ettringite has formed, it continues to grow expansively. Ifthe temperature of the system drops below approximately 15°C (59”F), Ettringite, through a series ofintermediate compositions is transformed to Thaumsite, (12), a complex calcium- silicate- hydroxide-sulfate- carbonate- hydrate mineral. Both Ettringite and Thaumsite are hydrous minerals. Without anabundance of water or excessive C,A they cannot form.

Typical mixtures of cement stabilized by-product gypsum contain between 3 and 8 percent cement.The remainder of the mix ingredients is gypsum and water. Therefore, it is correct to assume thatthere is a large supply of sulfate ions available to hydrate all the aluminate ions in the cement. Monosulfoaluminate, C,ASH1, will never form since there is no sulfate ion deficiency and consequentlythe phenomenon of reforming Ettringite in poland cement does not apply to by-product gypsumsystems. However, Thaumsite may form at temperatures below 15°C. Since both Ettringite andThaumsite are expansive products, extreme caution should be taken in the indiscriminate specificationof sulfate-resistant cements and mortars to be used for the stabilization of by-product gypsum.

For many years, fly ash (primarily Class C) has been widely utilized in concrete as a partialreplacement of cement. Presently, research is underway in Canada (CANMET) and at Texas A&M toincrease the weight percentage of fly ash used as a cement substitute from the typical 25 percent levelsto 50-60 percent for many structural and mass concrete applications (2). At these levels the mixturesare referred to as high-volume fly ash (HVFA) concretes. Aside from the work in Canada, GreatBritain and Australia, very little work on HVFA concretes especially those using Class F ash has beendone in the United States.

Up to the late 1970’s concretes containing fly ash also referred to as “pozzolanic cements” weregenerally proportioned by modifying traditional concretes containing portland cement, by replacing partof the cement content with fly ash. Since portland cement is produced at the expense of substantialamounts of energy, a partial substitution of portland cement by fly ash, which is generally available atcomparatively lower prices, would clearly represent a cost-effective use of both materials.Furthermore, there is evidence that fly ash is able to improve workability, durability and ultimatestrength and to reduce the heat of hydration creep and drying shrinkage (3). The incorporation of ClassF fly ash has also shown to significantly enhance sulfate resistance. This could permit the use ofHVFA concretes using cheaper Type I cements instead of the higher-cost, less available low C,A (i.e.high sulfate resistant) cements to stabilize by-product gypsums. Test results show that the HVFA

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laboratory concretes can meet or exceed the demands of most normal structural applications (4). It iswell known that during 1994 many concrete construction jobs had to be put on hold for lack of cement.It could be assumed that HVFA concrete could represent an attractive low cost alternatively reducing orextending the demand for concrete.

Two prime coats which have shown to work well as a seal over compacted stabilized gypsum baseshave been MC30 and RC250 cutback asphalts. Attempts to use emulsions on cement-treated bases haveproven unsuccessful since they tend to add additional water to the surface while it is in its initial curingphase and most vulnerable. The presence of this excess water increases the water to cement ratio andtends to create a weak shear plane about 0.5 inches below the surface during compaction subsequentlycompromising the integrity of the entire base when traffic is introduced or when deep freeze climatesare encountered.

e. Compaction and Sealing: Degree and type of compaction are critical factors affecting the ultimatestrength achieved in stabilized gypsum bases. The effect of compaction on both optimum moisturecontent and dry density and consequently on tensile and unconfined compressive strength has been wellestablished. The specification of a field density testing method should be coordinated with the localstate highway department. Similar to state standards for 7-day strengths, some deviation from standardpractice should be permitted in the determination of laboratory density values given the slow hydrationrates encountered when mixing gypsum with cement.

A set of recommended testing procedures and material selection for phosphogypsum mixtures criteriawere and have been shown to be applicable for other types of gypsums developed by Saylak et. al., (9).The laboratory compaction recommended for stabilized gypsum is Modified Proctor as prescribed byASTM D1557 which delivers 32.6 ft-lb/h? of energy to the specimen (12). The Texas Department ofTransportation uses its own Modified Proctor test and specimen configuration under Texas Method 113-E which only delivers 13.3 ft-lb/in3 of energy and would predict a higher optimum moisture contentand consequently achieve a lower strength than would be obtained using ASTM D1557. Using TexasMethod 113-E on stabilized-gypsum base mixtures tends to produce non-conservative decision criteriafor the design of roadbases by usually indicating an unnecessary need for more water and stabilizer.

Insufficient sealing of the base can make it susceptible to premature damage. Two treatments of astandard chip seal surface treatment or a one and a half to two inch thick highway department approvedhot mix asphalt concrete wearing coarse has been found to be effective.

Experimental Field Tests

Since 1988, TTI has constructed several experimental test sections directed towards establishing a materialsselection criteria, suitable mix design rationale and construction procedures to permit stabilized Phosphogypsumroadbases to perform on Texas State roadways. More recently the concepts generated out of these projects weresuccessfully demonstrated during the Summer of 1991 when a 2-lane, 300-foot long test section was placed atTexas A&M’s Riverside Campus, The roadbase consisted of 7-percent cement stabilized by-product gypsumsmixture with a 7-day unconfined compression strength of 450 psi. Post construction field tests are indicationthat the integrity of this road is sound, with no signs of incipient distress. Falling Weight Deflectometer dataindicate the roadbase, after 36-months of service, is still maintaining its strength.

A second experimental test section was built during the Summer of 1992 whose roadbase was comprised of a50/50 blend of gypsum and bottom ash; the latter at a ratio of 3 parts boiler slag to 1 part cinder ash. Themixture was stabilized with 7 percent of a high early strength sulfate resistant ((;A = 2.3) Portland cement andachieved a 7-day compression strength of 850 psi. A 22-month post-construction evaluation of the roadway wascarried out involving visual and state-of-the-art pavement performance monitoring technology. The results were

96

compared with those of the test section built in 1991 that did not contain bottom ash indicates the latter sectionto be stiffer with enhanced resistance to permanent deformation compared to the 1991 section. Except for some“block-type” surface cracking which appeared only in the 1992 section and was attributed to an unstabilizedexpansive subgrade, both sections are in excellent condition and performing well. It is suggested that careshould be taken with future roadbase mix designs not to overstabilize and that 7-day compressive strengths be inthe range of 450 to 550 psi.

Two additional road sections were built in 1993 using a Class C fly ash and a cement fly ash blend respectivelyas stabilizers. After two years these sections are performing well and show little sign of incipient failure.

The environmental impact of the 1991, 1992 and 1993 roadbases was evaluated through TCLP analysis ofmixture components along with ground water, surface water and leachates. The concentrations of chemicalcomponents tested were found to be either negligible or well below their respective EPA allowables.

Conclusion

Research on other types of by-product gypsums has continued following the EPA restriction in use ofPhosphogypsum. The results of laboratory and field test indicate that mix design rationale and constructionprocedures successfully demonstrated on these gypsums can applied to Phosphogypsum as well.

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References

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Chang, W. F. and M. I. Mantell, Engineering Properties and Construction Applications ofPhosphogypsum. Coral Gables, FL: University of Miami Press, 1990.

C. A. Gregory, D. Saylak, and W. B. Ledbetter, “The Use of By-Product Gypsum for Road Bases andSubbases”, Presented at the Transportation Research Board Meeting, Washington, DC., January,1984.

D. Little and W. W. Crockford, “Stabilization of Calcium Sulfate: Final Report for the Gulf StatesMaterial Company the Texas Transportation Institute, Texas A&M University,” May 1987.

Project No. 1690, A Grant to Texas A&M Development Foundation from Texas Utilities GeneratingCompany, 1985.

R. A. Taha, “Utilization of By-Product Gypsum in Road Construction”, Ph.D. Dissertation, TexasA&M University, December, 1989.

Mr. Dale Junghans, Personal Communication, Gulf States Materials, Inc., La Porte, Texas, July 16,1990.

Mr. Neal Anderson, Personal Communication, Mobil Chemical Company, Pasadena, Texas, March,1990.

C. A. Gregory, W. B. Ledbetter and D. Saylak, “Construction and Initial Performance Evaluation ofStabilized Phosphogypsum Test Sites”, La Porte, Texas, Report for Mobil Chemical Company by theTexas Transportation Institute, May 1984.

D. Saylak, R. Taha and D. Little, “Recommended Procedures for Sample Preparation and TestingStabilized Gypsum Mixtures,” In Procs.. of the Second International Symposium on Phosphogypsum:Volume II, Miami, Florida. December 1986, Bartow, FL: Florida Institute of Phosphate Research,January 1988.

“Beneficiation of Waste Calcium Sulfate,” TEES Study No. 32131-70500-CE sponsored by TexasHigher Education Coordinating Board (Dr. D. Saylak, P.I.), (on-going).

C. Wong and M.K. Ho, “The Performance of Cement-Stabilized Phosphogypsum as Base on StateHighway 146, La Porte, Texas”, State Department of Transportation, Research Section, Austin, Texas,October 1988.

D. Hunter, “Lime-Induced Heave in Sulfate-Bearing Clay Soils”, Journal of Geotechnical Engineering,ASCE, 114, no. 2 (1988).

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POLK COUNTY EXPERIMENTAL ROAD

WILLIAM C. KENLEYCOUNTY ENGINEER

DIVISION OF PUBLIC WORKSPOLK COUNTY, FL

********

Author: William Kenley, Polk County.

Mr. Kenley has been County Engineer of Polk County since 1984. Before becoming County engineer, hespent seven years as Assistant County Engineer in charge of road and bridge maintenance and construction. Mr.Kenley also spent 22 years in private practice with consulting engineers doing a wide variety of civilengineering work, including supervising design and construction of subdivisions, industrial sites, and publicworks projects. He is currently the southeast Regional Vice President of the National Association of CountyEngineers and past president of the Ridge Branch Florida section of the American Society of Civil Engineersand the Florida Association of County Engineers and Road Superintendents. He has served terms as Chairmanof the Florida Advisory Committee to Polk County MPO and has served on the Florida Technology TransferCenter Advisory Committee.

Mr. Kenley has a Bachelor’s degree in Civil Engineering from the University of Illinois and is registered as aProfessional Engineer and a Professional Land Surveyor in Florida and Illinois.

********

In October 1986, the Polk County Division of Public Works built an experimental road utilizing phosphogypsummixtures. This one and one-half miles of secondary road is located south of US 98 and east of Fort Meade (1).

The experimental project was to provide alternate methods of rebuilding county and other secondary roads inFlorida. It was intended to provide comparable or better material to repair or replace existing roads with thebest possible utilization of locally available aggregates.

Construction practice in building these secondary roads consists of mixing generally granular soil subgrade withfine grained soils transported to the site. Granular soil such as sand is abundant throughout Florida. However,lack of adequate source of fine-grained soils such as clay, has been a major concern of builders of such roads.Furthermore, it has been found that roads built with clay-sand mixtures tend to be greatly affected by changes inmoisture regime, tending to become soft and muddy during the long and rainy summer. This prompted the PolkCounty Division of Public Works to take the initiative in finding alternative methods of rebuilding their roads.

The design and testing of the road was a collective effort of the University of Miami, the Florida Department ofTransportation and Polk County. The road was built by the Polk County Division of Public Works, andphosphogypsum used for the project was supplied by the US Agri-Chemicals. The experimental project calledfor a thorough environmental impact investigation which include pre and post construction sampling of air, soiland groundwater. Environmental monitoring, conducted by the University of Miami and the Florida Institute ofPhosphate Research in cooperation with the Florida Department of Environmental Regulation and the FloridaDepartment of Health and Rehabilitative Services, detected no significant environmental impacts (2)(3).Construction was as follows: The existing road surface layer was levelled with a motor grader and compacted.

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Phosphogypsum at its natural moisture content was delivered by means of dump trucks and evenly spread tomeet the appropriate lift thickness. A pulvimixer was used to thoroughly mix the phosphogypsum with thesubgrade material. Following the mixing phase, the road cross-section profile was shaped according to thedesign drawings. The road was then compacted and the asphalt laid down atop the phosphogypsum base.

The road has been open to traffic since October 1986. The experimental project has successfully demonstratedthe use of phosphogypsum in road construction. Evaluation of the construction crew was as follows:

1. Phosphogypsum can be used as a binder for base course mixture.

2. Phosphogypsum mixtures are easier to work with than clay mixtures.

3. Operation at cost including equipment time for constructing phosphogypsum roads are lower than thatof clay roads.

4. Rain storms during construction did not cause excessive delays because the compacted mixture did notabsorb water to any great extent.

5. Shrinkage cracks, frequently occurring in clay roads, did not appear in this construction.

6. The stability of compacted phosphogypsum mixtures is superior to that of clay mixtures.

To date, Parrish Road has performed as well as any traditionally constructed road.

In order to accurately determine the cost of building a secondary road utilizing phosphogypsum, the Universityof Miami Department of Industrial Engineering prepared a detailed analysis and comparison of the constructioncost for Parrish Road and two similar roads built with traditional materials (4).

The cost analysis (Figure 1) makes it obvious why Polk County would use phosphogypsum for secondary roadsif not prohibited by EPA regulations. Polk County faces the same problems faced by the other counties and eventhe state, never having enough money to build and adequately maintain their road systems. While we would notwant to claim that every road project would have the same cost advantage as Parrish Road shown in this graphiccomparison, we are convinced that our road building and maintenance monies would go much farther usingphosphogypsum.

Earlier this year I read a newspaper article (5) that estimated that state transportation funding had a projectedlong-term short fall of up to $30 billion and I cannot help but wonder if the planned research onphosphogypsum primary road construction that was curtailed after the EPA prohibition on phosphogypsum use,would have provided the answers that would enable our state not only to maintain but to actually upgrade ourexisting highway system, without the need for additional tax dollars.

1 0 0

Cost Comparison: Traditional Road Vs. Phosphogypsum _

$98.339

$129,320

Material 36.9%

Equipment 33.4%

Tanner Road Windy Hill Parrish Road

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References

1. Kenley, W.C. and W.F. Chang. “Polk County Experimental Road”, In Proceedings of the SecondInternational Symposium on Phosphogypsum. Miami, Florida, December 1986, Bartow, FL: FloridaInstitute of Phosphate Research, 1988.

2. Chang, W.F., D. A. Chin, and R. Ho, Phosphogypsum for Secondary Road Construction, Bar-tow, FL:Florida Institute of Phosphate Research, 1989.

3. Nifong, G.D., and J.K. Harris, Environmental Monitoring of Polk and Columbia CountiesExperimental Phosphogypsum Roads, Bartow, FL: Florida Institute of Phosphate Research, 1993.

4. Sumanth, D.J., M.A. Carrillo and S. R. Koganti, “Economic Analysis in Constructing a SecondaryRoad with Phosphogypsum Using Total Productivity Modeling, " In Proceedings of the SecondInternational Symposium on Phosphogypsum. Miami, Florida, December 1986, Bartow, FL: FloridaInstitute of Phosphate Research, 1988.

5. Adair, Bill, “Across the state the road ahead isn’t smooth.” St. Petersburg Times, March 7, 1995, p.1A.

1 0 2

PRELIMINARY INVESTIGATION OF PHOSPHOGYPSUMFOR EMBANKMENT CONSTRUCTION

ROBERT HOSTATE SOILS MATERIALS ENGINEER

FLORIDA DEPARTMENT OF TRANSPORTATION

* * * * * * * *

Author: Robert Ho, Florida Department of Transportation.

Dr. Ho is head of the Materials and Research Section of the state DOT where he has spent more than 24 yearsworking with soils, materials, aggregates and road construction problems statewide as well as testing andvariability studies for specification preparation. Dr. Ho also spent six years with geotechnical consultingengineers in Hong Kong and Canada. He has published reports on using phosphogypsum to constructexperimental roads and embankments.

Dr. Ho earned a Bachelor’s of Science degree in Hong Kong, a Master’s degree in English at McGill Universityin Canada and a Ph.D. at the University of Florida.

*********

Over the years phosphogypsum, a waste by-product of phosphoric acid production, has been accumulating atphosphate mining sites in Florida. This waste material has been used as base and fill material for local haulroads in the phosphate mines. It is believed that this abundant waste material can provide an economical sourceof fill for some suitable local projects.

As part of a research program on the investigation of waste materials for use in highway construction, the StateMaterials Office in 1982 conducted a preliminary study on phosphogypsum as a potential fill material inembankment construction.

Laboratory Tests

Seven sources of phosphogypsum from various mining sites around the state were selected for the study. Acomprehensive laboratory testing program was performed on samples from all the sources. These tests include:

1. Grain size distribution2. Plasticity tests3. Specific gravity4. Moisture - density relationship (how well they compact)5. Limerock bearing ratio (LBR) and triaxial compression tests (for strength)6. Permeability7. Gypsum content and pH (acidity)

All tests were conducted in replicates of three to determine the inherent variability between samples.

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Test Pit Study

The phosphogypsum was placed in the test pit and compacted to a specified density. A cyclic load of 50 psi(one cycle for every 2.5 seconds) was applied through a 12-inch diameter circular plate. This is to simulatemoving traffic wheel load. Ten thousand cycles were applied in an 8-hour day. The settlement of the platetogether with the number of applied load cycles were recorded to determine the performance of the materialunder traffic load. Results were plotted on a semi-log plot.

Test Results and Discussion

Test results indicated engineering properties of phosphogypsum vary from source to source. These differencesare manifested in their grain size distribution, percentage of fines, bearing strength and deformation under cyclicloading.

According to the soil classification procedure used by all State DOT’s, phosphogypsum is classified as a A-4silty soil with a rating of fair to poor as a subgrade material. Florida DOT design standard only permits A-4silty soil be used at least 5 feet below grade elevation and above the water table. That means that onlyembankments greater than 5 feet above the water table can phosphogypsum be used provided that leachatethrough the embankment will not affect water quality or other environmental constraints.

One field problem that has not been investigated is the moving and handling of large quantities ofphosphogypsum. Because of the silty nature of the material, it is very sensitive to moisture during compactionespecially on the wet side of optimum moisture content. Handling and placing of this material should be avoidedduring the rainy season.

This preliminary study on unstabilized phosphogypsum indicated that the material may be used in embankmentprojects provided environmental constraints can be met and also be competitive with local fill material. Researchdone by others have indicated that phosphogypsum stabilized with cement may be used as a roadway base.

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LOAD APPLICATIONS

THE USE OF PHOSPHOGYPSUM INROAD CONSTRUCTION

BY

J.B. METCALFINSTITUTE FOR RECYCLABLE MATERIALS

LOUISIANA STATE UNIVERSITY

* * * * * * * *

Author: J.B. Metcalf, Louisiana State University.

Dr. Metcalf was appointed Freeport-McMoRan Chaired Professor of Engineering at Louisiana State in 1992and joined the Institute for Recyclable Materials, which is conducting a research program to investigate theutilization of phosphogypsum. Dr. Metcalf has experience in engineering and road construction worldwide. Hisinterest is in low cost roads, non-standard pavement materials, pavement design, construction quality control andtechnology transfer. He has worked in the United Kingdom, Canada, and Australia where he was materialsengineer with the Queensland Main Road Department from 1964-1969 and was appointed Deputy Director ofthe Australian Road Research Board in 1975. He is the author of some 80 technical papers and has been thekeynote speaker at national and international conferences. He has acted as a consultant/advisor to the UnitedNations, the World Bank, the Australian International Development Assistance Bureau, the Kingdom of SaudiArabia, Australian Federal and State Road Authorities, and various branches of industry. Dr. Metcalf iscurrently an advisor to the Federal Highway Administration.

********

The material

Phosphogypsum is a tine grained material composed of crystals of gypsum (Calcium Sulphate Di-hydrate) withsmall quantities of impurities, usually less than 20 per cent, of which about half is silica. The pH ranges from3-5. Phosphogypsum has a specific gravity of 2.35, close to that of soils. On average about 75 per cent of thematerial will pass the No 200 sieve.

Phosphogypsum can also be processed for recovery of sulphuric acid to yield a slag by-product. This materialconsists mainly of iron oxides, calcium silicate compounds and an amorphous glass and is formed as irregularrough and honeycombed aggregate of about 30 mm maximum particle size. It is non plastic.

The Institute for Recyclable Materials has identified applications of Phosphogypsum (1).

The road engineering properties

Phosphogypsum can be classified as a silty soil(2), an A-4 or ML soil, with little or no plasticity. It is availablein bulk from stockpiles at several locations in the USA, and overseas. In the stockpiles it contains some water,often in the range from 8-18 percent and varying with depth, but can usually be taken from mature stockpiles ina form very similar to a damp soil. The fact that it can be stockpiled to substantial heights indicates that it is notentirely unsuitable for fill and embankment construction but any silt-like material is inherently unstable,particularly when water is present. It is easily eroded, relatively impervious and very susceptible to frost heave.

111

It can be compacted to a dry unit weight of between 80 and 100 pcf at optimum moisture content of 12-20 percent, when a CBR (California Bearing Ratio) of about 30 can be measured (3). However, because the materialis soluble it is not suitable for road pavement construction in the untreated state.

A number of laboratory studies of methods to improve me material for use in roads have been conducted usingcement stabilization. In this process, a small (4-15 per cent) amount of cement is mixed with soil, usually inplace, and the mixture is compacted and cured. Full scale experimental road sections also have been placed, inFlorida and Texas (3,4).

The critical properties required of cement stabilized road base are compressive strength and durability; whichare very closely related. A typical specification for cement stabilized road base requires that the compressivestrength of the mix, after compaction and curing, reach a minimum figure. The Louisiana Department ofTransportation and Development, for example, until 1992, specified a minimum of 250 psi after 7 days. TheDepartment now requires a minimum cement content for soils which is prescribed by soil type and Parish,usually between 8 and 12 percent, but up to 15 per cent is necessary for some soils. At these cement contentsthere is little doubt that cement stabilized phosphogypsum will meet the previous strength criteria (4).

Thus most studies have sought to determine the appropriate mix to achieve the required compressive strengthand to evaluate the treated phosphogypsum against other specification criteria. The results achieved withphosphogypsum and cement alone may be marginally low when the early (7 day) strength is considered, andways to improve early strengths have included the addition of fine grained soils or sand to the mix, or morerecently, the use of a cement set accelerator. Both methods proved effective and it has been demonstrated in thelaboratory that cement stabilized phosphogypsum can meet the usual specification requirements for road base(6).

The slag will meet LADOTD specifications for aggregate and EPA toxicity and TCLP leachate standards. Afeature of the aggregate process that it reduces the radon emanation (7). The material has been shown to meetLADOTD hot mix asphalt requirements with 6.5 % binder (8). More work is necessary to quantify stripping andfrictional parameters.

The use of many natural, by-product or recycled materials for road construction is constrained by conservativespecifications and, whilst the first evaluation of any material must be against the existing standards, there is alsopotential for the examination of the standards and modification of the requirements to reflect our increasingknowledge of the response of pavements to traffic loads (9). A major change in pavement design is beingimplemented in which the structural properties of the materials are evaluated, in the laboratory, under repeatedloads to better simulate the real world. The measurement of the ‘resilient modulus’ of materials is becoming theaccepted way of determining the structural capacity of road base materials and recent studies have followed thisnew approach, to establish appropriate testing protocols and design acceptance (10).

The research conducted at IRM showed the resilient moduli measured for cement stabilized phosphogypsum areusually lower than for most soil cement mixes but still adequate for road base construction. Studies of theaggregate resilient modulus are about to commence.

The problems

There are two concerns; the potential for dissolution and/or leaching of the mix, and the potential for volumechange due to changes in water content and/or chemical reaction.

Laboratory tests show that leaching from cement stabilized phosphogypsum is well within EPA standards evenunder the extreme physical degradation applied in the TCLP test (11), in fact, the cement contributes moreheavy metals than the phosphogypsum. Compaction and cementation effectively reduce the leachability of saltsthus it appears unlikely that leaching of any potentially harmful component of the cement stabilized materials

112

will occur, even where the road base is exposed to free water (3). The water environment under a road does notchange very quickly because most construction materials have low permeability, and road surfaces are designedto be impermeable. The radon emissions are also reduced by compaction, which reduces the air and waterpermeability of the mass.

The potential for volume change is also constrained by the usually stable environment but there is a reactionbetween cement and phosphogypsum which forms the mineral ettringite, and in so doing can increase thevolume of the mix. The potential for disruptive expansion is now being investigated but it may well be that thiseffect could offset an existing problem with cement stabilized soils, which is the formation of cracks due thetendency for cement treated materials to shrink.

Both leaching and volume change can be significant factors affecting the durability of cement stabilizedphosphogypsum as road base and require further study.

The potential

One mile of secondary road will use about 5000 tons of phosphogypsum.

Laboratory tests show that cement stabilized phosphogypsum can meet typical specification requirements forcement stabilized soil for road bases at cement contents similar to those for Louisiana river silts. However, it islikely that most potential users will require some evidence of a successful application in practice before adoptingstabilized phosphogypsum for bases. The trials in Florida and Texas were useful in this regard but the lack offollow up, caused in part by EPA regulations, has decreased the impact of these demonstrations.

It will require new full scale experiments to convince users that cement stabilized phosphogypsum roadpavement bases can be effectively and economically constructed and that they will have adequate performance.Estimates of the design lives of stabilized phosphogypsum pavements were therefore made for a possible fullscale experiment to be built within the Louisiana State University agricultural area (12). These estimates werebased on a 12 per cent cement content for the phosphogypsum, selected to exceed the strength attained with aten per cent river silt soil typical of the Baton Rouge area. A subgrade of clayey sand, with a CBR of 2-5 wasdetermined, and a crushed limestone base was selected for comparison. The test results for the cement stabilizedphosphogypsum showed a compressive strength of c. 450 psi at 28 days, which allowed for the interval betweenconstruction and trafficking of the road.

Assuming typical structural coefficient values for the limestone and asphalt surface courses and interpreting thestrength and resilient modulus data for the phosphogypsum in terms of structural coefficients allowedcomparable designs to be developed. Adopting the LADOTD standard base course thickness of 8.5 in, designswere compared using the AASHTO procedure to estimate pavement life. The results showed that for a roadcarrying 900 vehicles per day (a typical secondary road) for 20 years, cement stabilized phosphogypsum wouldbe a viable competitor to the crushed limestone bases currently in common use.

The next steps

There remain three areas of study before cement stabilized phosphogypsum can confidently be marketed as roadbase. First, a more comprehensive study of the variability of phosphogypsum is needed, to ensure that aconsistent product can be offered. This will require a laboratory program to measure strength and moduli for asubstantial number of samples. Second, a better understanding of durability, particularly in relation to possibleleaching and volume change effects will require further laboratory study. Third, one or more fielddemonstration projects will be necessary. Such demonstrations could take the form of test roads, subject tonormal or some form of accelerated traffic, the former is slow the latter expensive, or an accelerated full scaletest using the LTRC Pavement research facility.

113

The slag aggregate should now be assessed in the laboratory for suitability as unbound base aggregate and forcement and bitumen stabilized applications. The possibility of full scale trials of slag aggregate should beconsidered when a supply of the material is available.

Finally, the results of the studies will need to be assembled into an implementation package, including designguidelines, construction specifications, QA/QC procedures and a training manual.

The bottom line, as always will be the comparative economics of stockpiling versus utilization, or other disposalpractice.

References

1. Taha, R. and R.K. Seals, “Applications identification of phosphogypsum” Report I-91-3D, Institute forRecyclable Materials, 1991.

2. Taha, R., R.K. Seals, M.E. Tittlebaum, W. Thornsberry and J. T. Houston, “The use of by-productphosphogypsum in road construction,” Transportation Research Record 1345, 1992.

3. Chang, W.F., D.A. Chin and R. Ho, Phosphogypsum for secondary road construction: final report forthe Florida Institute of Phosphate Research, 1989.

4. Wong, C. and M.K. Ho, “The performance of cement stabilized phosphogypsum as base - StateHighway 146, La Porte, Texas, ” Report DHT-11, Texas Dept of Highways and Public Transportation,Austin, TX, 1988.

5. Ong, S., J.B. Metcalf, R.K. Seals and R. Taha, “Unconfined compressive strength of variouscement-stabilized phosphogypsum mixes, ” Transportation Research Record 1424, TRB, Washington,1993.

6. Gutti, S., J.B. Metcalf and R.K. Seals, “Material variability and the influence of admixtures on thestrength and volume change properties of cement stabilized phosphogypsum,” Presented to 74th AnnualTRB meeting, 1995.

7. Taha, R. and R.K. Seals, “Engineering properties of phosphogypsum based slag aggregate,”Transportation Research Record 1345, 1992.

8. Taha, R. and R.K. Seals, “The use of phosphogypsum-based slag aggregate in hot mix asphalticconcrete,” In Proc. ASCE Session on Utilization of Waste Materials in Civil Engineering Constructionpp202-216, 1992.

9. Metcalf, J.B. “The use of naturally occurring but non-standard materials in low cost roadconstruction,” Geotechnical and Geological Engineering 9 (1991): 155-165

10. Pericleous, M.I. and J.B. Metcalf A preliminary study of the resilient modulus of cement stabilizedphosphogypsum, ASCE Jnl of Materials, ASCE (in Press), 1995.

11. Tittlebaum, M.E., H. Thimmegowda, R.K. Seals and S.C. Jones, “Leachate generation from raw andcement stabilized phosphogypsum” Presented at 74th Annual TRB meeting, 1995.

12. Gerrity D.M., J.B. Metcalf and R.K. Seals, “Estimating the design life of a prototype cement-stabilizedphosphogypsum pavement, ” Transportation Research Record 1440, TRB Washington, 1994.

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CRITICAL, DOSE AND RISK ASSESSMENT FOR USE OF WASTE PRODUCT PGIN ROAD CONSTRUCTION

BY

ANTHONY C. JAMES, Ph. D.ACJ & ASSOCIATES

RICHLAND, WA

********

Presenter: Anthony C. James, ACJ & Associates.

Dr. James has recently become an independent consultant after holding the position of Associate Professor in theCollege of Pharmacy at Washington State University. Prior to this Dr. James was the Chief Scientist in theOccupational and Environmental Health Protection Section of the Health Physics Department at Battelle, PacificNorthwest Laboratories. At Battelle, his primary research interest was in the development and application ofdosimetry of body tissues in humans and experimental animals, in order to address issues involved in settingpractical standards for radiological protection, and in relating cancer risks to environmental conditions ofexposure. Before joining Battelle in 1988, Dr. James had 17 years of research experience, much of it relating toradon, at the National Radiological Protection Board, Chilton, United Kingdom.

Dr. James has a B.Sc. in physics from University College in London and received the Ph.D. degree from theRoyal Free Hospital School of Medicine in London in 1969.

********

Paper not available. The following is a transcription from video of Dr. James’ presentation at the Forum.

* * * * * * * *

EPA, in their assessment, assumed that the concrete surface of the road had crumbled and had been removed.You just mentioned that it may not be a very sensible thing to assume. What we’ve got is the roadbed, eitherwith the contaminated concrete as the slab or with the contaminated concrete, being removed and replaced withfresh concrete. The dimensions of the road base are about the same as the typical fill in the slab-on-gradehouse. We have not gotten very far with the specific calculations for this case, but it looks from our experiencewith the agricultural scenario that the numbers that EPA came up with, in terms of doses compared withconcentrations, or the proportion of PG that is used in the roadbed agglomerate, relating those to indoorexposures are going to be in the right ballpark.

There are a couple of factors that do have an impact on this. EPA tries to assess the effect of moisture contenton the emanation efficiency and the amount of radon that comes into the structure. A paper (Rutherford et al.,1995) was published in Canada in Health Physics just a couple of months ago which is very useful in thisanalysis. What was looked at was the effect of water saturation on the emanation coefficient of three differenttypes of PG. One of the types studied was Florida PG, another type was from Idaho, and the third was fromTogo, which is in Africa. Several samples were studied from each source and the results were really amazingly

115

internally consistent. There does not seem to be too much dispute about the emanation coefficient that wouldbe most appropriate to apply in these assessments. There also is a consistent picture of what happens withwater saturation. Dry PG has a de-emanation coefficient that is relatively high but you notice that it is about afactor of 2 lower than the EPA standard assumption of 30 % . At moderate saturations the de-emanationcoefficient drops further, but as the saturation goes up to 100% emanation becomes more efficient. It’s unlikelythat the 30% value assumed by the EPA would be realistic. That lower emanation coefficient was folded intothe calculations that I showed you the results of earlier on. It’s one of the factors that caused the assessmentthat was done in a very different way, including other determining physical factors, is one of the things that ledto the same relationship between subsurface radium content and radon exposure indoors. So its fortuitous, but ithappens to yield very similar numbers to EPA’s.

We heard about size fractionation. These values apply to Florida PG. The bulk PG is the average for thewhole sample. Several samples were size classified by settling in the coarse fraction with particles larger than50 micron, medium fraction between 20 and 50 micron. You see that the size fractionation does not have muchimpact on the de-emanation efficiency. However, for the very fine particles less than 20 microns the emanationefficiency is quite substantially larger. This is not an important observation, however, because there is only acouple percent of the actual radioactive content present in the fine aggregate. So the emanation coefficient ispretty well determined and I think it agrees with what Chuck Roessler found quite some time ago.

In terms of the gamma dose calculation, it really depends on whether or not an additional level of shielding isput on; whether you come down below EPA’s estimates or whether you come up with about the sameconclusion. If we can sum up the position for the assessment of risk of building a home on a roadbed, in termsof EPA’s criterion for acceptability, which is a lifetime risk coefficient of 3 in 10,000, it does not look like avery good prospect. So it’s a different situation for the road building case and for the agricultural use. If youtake reasonable application rates for agricultural use, then the calculated doses come down within EPA’sacceptability criteria. But if you build a house on a roadbed, whether or not you leave the concrete in place;it’s worse if you leave contaminated concrete in place rather than putting uncontaminated concrete on top, butwith the astringent criteria of 3 in 10,000 as an acceptable lifetime risk, it will be hard to overcome that test ofacceptability.

116

Phosphogypsum Fact-Finding Forum! Florida State Conference Center, Tallahassee, FL, December 7.1995

Detail of Floor and Wall for Florida Slab-on-Grade House Showing Backfill and Native Soil

t= 4

(Revzan et al., 1993)

I Concrete

Block wall 0.19 m-A

r - 0.028 m

b-O.45 m ----+

indings 0fBattelle’s Study for Use of ste Product PG in Road Coustruction

Assuming no site excavation and no backfill with “uncontaminated” material, then EPA has overestimated lifetime risk from direct gamma irradiation by about a factor of three. F 03 ’

With these same assumptions, EPA’s calculated incremental lifetime risk from indoor radon is about right, but for a much lower ventilation rate of 0.5 sch.

A 30-cm thick backfill with “uncontaminated” material would give an incremental lifetime MIR from PG in an old roadbase would not be significantly lower than the “aweptables9 value of 3 in ‘10,000.

-From video, transcript of questions and answers of Construction Panel discussion:

POLICY PANEL QUESTIONS TO CONSTRUCTION SPEAKERS

OHANIAN: And now we have some time for the panel to ask some questions of the panel who just presentedtheir papers so please have a go at it. Who wants to go first?

SMITH: I’m not sure this is a question but I would make an observation, having some knowledge of roadconstruction for 35 years. I think it’s interesting to note, and I think its a point that this group needs toconsider, there’s quite a bit of variation in the way all these gentlemen looked at things. And I really doubt thatTexas ***** break in tape ******* but I think it suggests that if you are going to get into road constructionthere’s a lot of barriers between the various states, because we do things differently, and those would trace backto native materials, and here we’re dealing with a different animal. So I don’t really have a question but Iwanted to make that comment.

* * * * * * * B R E A K I N T A P E * * * * * * * * * * * * * * *

SAYLAK: . . . . Texas acceptance criteria for stabilized bases has been this magic number 650 psi in 7 days.Illinois requires 650 psi in 14 days. When you look at where this magic number came from, you find out that itwas based on a 2 sigma survivability for freeze thaw testing. You need to look at your various locale to findout if you need to be held to a 7 day 650 psi. That’s why when we really looked into this, we found out that allwe needed was 400.

SMITH: I wasn’t referring to the psi, I was referring to the so called coefficient which is used in design.

SAYLAK: Oh, the structural coefficient?

SMITH: Yes.

SAYLAK: Okay.

BANDY: Earlier this morning there was a question that came up from the panel. I think Mr. Coleman askedthe question regarding centrifuging of the gypsum to remove radioactivity. From the data that Dr. Jamespresented a few minutes ago where he showed the fines had more radon emanation, although that is the case,but that is a very small contribution to the total picture. If I conclude that removing those fines would changethe radon emanation very much from the PG, would I be correct?

YOUNG: Though I am no engineer, it seems reasonably demonstrated to me that there can be standards indesign criteria developed to make this material very suitable, even given the distinctions regionally and with thedifferent soils. The concern for EPA would have to be in terms of the risk assessment and the health risk. ButI’m not clear even what EPA’s real concern is, with regard to using the material in a road base. I hear yousuggesting that we need to somehow meet a standard assuming someone would build a house. Yet I can’timagine any local or state government allowing someone to build a house on a public road, and I can’t reallyenvision it on a private road. What are the issues that we really need to be concerned about? Is it the leachingof the materials, or is it the radiation? I thought that ventilation and just the exposure to the air would take careof the risk to individuals. If that does not take care of it, what mitigation can be used to address this particularconcern?

1 1 9

JAMES: Well unfortunately in this case you’ve got two sources of radiation. You’ve got external gammaradiation so if you mitigate to prevent radon from coming in you still don’t reduce the direct gamma exposure.It would be very difficult to do that unless you remove the road. If you actually dug up the road under thehouse then that would be acceptable but that would be a pretty costly thing to do, wouldn’t it?

YOUNG: Well I guess I’m assuming that we’re not going to build a house. So lets address it from a differentperspective and say okay, the rules say you just can’t build houses on these roads. Then what is the risk to thetraveling public or the public that just might be in the area of the road.

JAMES: The EPA themselves determined that the only significant risk is to someone who builds a house. Andthat they used as a justification in their own thinking to banish use in road construction. So they’ve alreadylooked at the other potential sources of exposure and they are negligible compared with the exposure to someoneliving in a house built on a road bed. So it is really a political issue. You just have to find some way ofconvincing them that it’s an artificial limitation on the use of PG. But if they insist on applying the 3 in 10,000risk criterion, I think their sums are good enough that use of 2 to 1 dilution PG in roadbed would preventapplication of PG for road building.

OHANIAN: (To James) Isn’t the issue that they are concerned that 100 years, 500 years, 1000 years from nowsomebody will go back and do something like that? Build a house. It’s the same kind of argument as thenuclear waste issue. That 10,000 years from now someone will go and dig up the nuclear waste unknowinglyor knowingly. Isn’t that the same situation with the house building on the roadway?

JAMES: Yes, I think its exactly the same.

SMITH: (To James) Isn’t the EPA risk assessment based on some level of radiation in the material to beginwith? Someone else may have to answer the second part of my question, but from what little I know there is alarge sum of PG out there that will not have that level of radiation.

JAMES: Yes. The level of radiation we looked at is about 30 pCi/g so its at the top end of the range. So itwouldn’t prevent use of northern Florida gypsum I presume.

SMITH: Many of these materials have been stacked for numerous years. When we looked at these materials itseemed to me that those were little or no threat, from a radiation point of view. So there has to be somedissipation within the stacks themselves and yet what I’m hearing is that the EPA regulation tends to overlookthat. Is that correct?

JAMES: Yes. The ruling is based on a hypothetical concentration.

GLASSMAN: A general question. In Florida most of the highway construction is co-mingled funding with thestate government and the Federal Highway Administration, which brings Federal Highway into the issue. I’mjust curious if anyone knows the status right now of the Federal Highway’s position on this or what work hasbeen done through the state associations, AASHTO (the American Association of State Highway andTransportation Officials) Or if AASHTO and the Federal Highway might be working together with the EPA onthis issue at this time? Is there any discussion going on? Is this being an AASHTO policy position, or is thereany discussion at the national level about this?

SAYLAK: It’s not so much a policy issue. I think that what has happened is that the search for a way of usingalternate aggregate materials has caused a lot of the construction industry to go to something other thanphosphogypsum. It’s not that they are not using a by-product gypsum. They are. Its just the fact that there isthis one particular entity (PG) that has all the technology to perform just like all the other stuff and at least forthe moment, it is not available for use. Once that burden was taken off, I don’t see where either state orfederal would have any problems incorporating that into their programs.

120

SMITH: I’ll comment on that last question. You kind of put in perspective the Federal HighwayAdministration in its relationship to us. Generally each state will decide for itself what it wants to do, so theonly knowledge that I have of any major activities of the Federal Highway Administration is currently ****break in tape ****** which is looking into all the waste, as I recall, PG is on that list. And I think their goal isto summarize things and to offer opportunities to other states. They tend to encourage us rather than obstructus, so I don’t think they have a general policy on it. But if we want to use something as a state then it wouldbe up to us to take it to the Federal Highway Administration. And generally we’ve been very successful. So ifwe wanted to use these materials and felt like we could use them I don’t think that’s an obstacle. I think theywould encourage it. Again though you have to consider economics in all this.

1 2 1

THE INTEGRATED APPLICATION OFENVIRONMENTAL EPIDEMIOLOGY AND HEALTH RISK ASSESSMENT

TO PHOSPHOGYPSUM EXPOSURE

TIMOTHY C. VARNEYVICE PRESIDENT, ENVIRONMENTAL RISK MANAGEMENT

CHASTAIN-SKILLMAN, INC.

* * * * * * * *

Author: Timothy Varney, Chastain-Skillman, Inc.

Dr. Varney is Vice President, Environmental Risk Management with Chastain- Skillman. His work focuses oncomprehensive contamination assessment, environmental epidemiology and health risk assessment related to thegeneral environment and man-made structures. Dr. Varney has worked extensively the past 24 years throughoutFlorida and the eastern United States on issues related to environmental contamination, health risk assessment,environmental and occupational exposure assessment, risk management and regulatory compliance in the publicand private sectors. He has also appeared as an expert witness in courts of law and public hearings in mattersinvolving environmental contamination and occupational exposure. He is also an adjunct faculty member at theUniversity of South Florida College of Public Health where he lectures in environmental chemical fate,exposure measurement and hazardous waste management.

Dr. Varney received a Bachelor’s degree in Geology with an emphasis in Geochemistry from the University ofSouth Florida and a Master’s degree in Public Health from the university’s College of Public Health. He hasrecently completed the requirements for a Ph.D. in Public Health from USF as well.

********

During the past decade the general public has become increasingly sensitive to all forms of toxicant exposure inthe general environment irrespective of the true health risk associated therewith. The true risk associated withsuch exposures has now been replaced by the perceived risk and this problem has been accentuated by scientists,managers and regulators who have oftentimes sent mixed signals about a subject that everyone agrees is highlycomplex. Most members of the public are so overly concerned by even the most trivial exposures to chemicalsand radiological agents in the environment that it has even become difficult to design and implement remedialmeasures when they are truly needed. The net result is a confused, scared and sometimes hostile public that seesindustry and big business as the source of the problem. While this may have been the historical case in someinstances, business practices have changed greatly but public perception has not. Clearly, a fresh perspective isneeded, one that places environmental exposures in an objective context with health-related risks and a changingregulatory agenda--a perspective the public can understand and trust.

Historically, from a regulatory context, the approach to protecting the public has relied on setting maximumcontaminant levels (MCLs), action levels and remediation levels for toxicants in the environment basedpredominantly on animal models and occupational cohort exposure measurements. In general, as a startingpoint, there is nothing terribly wrong with this approach. However, approximations of health-related risks havetraditionally relied on very conservative upper bound (95 % confidence interval) deterministic methods aimed atprotecting the most highly exposed and most sensitive individuals in the population. From a purely humanisticviewpoint it is hard to find fault with such an approach. However, many individuals in the scientific communityand the business sector have argued that such an approach is not objective with respect to the true underlyingdistribution of risk and, most importantly, the distribution of uncertainty related to the component factors of

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risk. Moreover, it is also felt that this approach has often led to the misguided expenditure of resources for theremediation of low risk sites or the over regulation of industrial wastes that could be safely handled by othermethods. However, the conventional manner by which these problems have historically been addressed cannotsimply be abandoned. Rather, the old approach must be replaced by a new paradigm that also embraces methodsin environmental epidemiology and probabilistic risk analysis so that we may move towards a more logicalhandling of the problem.

Environmental epidemiology can be generally defined as the study of those environmental factors having aninfluence on the origin and distribution of disease in the general population. Such studies may take the form ofdisease or injury recognition in conjunction with an evaluation of the subject population and potential causalfactors relative to time and space. Conversely, the study may also proceed from the opposite direction beginningwith the exposure factor and working forward to a potential health endpoint. Obviously there are strengths andweaknesses inherent in both approaches. One of the most pressing aspects of such studies, however, is thechallenge of obtaining adequate exposure data. This challenge becomes even greater when one considers thatexposures to environmental toxicants are often specified in the parts per million or parts per billion range.However, several investigative methods are available and applicable to environmental epidemiologic studies inassociation with exposures to phosphogypsum in nearby communities and the general population.

The first step in this research process would typically involve identifying those constituents of phosphogypsumthat exhibit toxicant behavior of specific environmental concern. These might involve both chemical andradiologic agents that have been previously determined to be mobile in the surrounding environment, such asheavy metals and radon daughters. The next step would involve defining the preference for environmentalpartitioning, particularly as it relates to air, soil and water. Most importantly, is there a preferential exposurevehicle such as groundwater or ambient air, and is there a definable population at risk along this pathway? Ofparamount importance, is there biologic plausibility for a specific disease endpoint? For instance, if one isconcerned with radiologic agents, then the disease endpoint of interest might well be the most radiogenic formsof cancer. For study purposes these could include the leukemias and cancer of the thyroid gland, or the listcould be expanded to include cancers of the bone and lung. These cancers are offered as examples of one groupof disease endpoints that could be considered. Obviously, other chronic and/or acute diseases and adverse healthoccurrences can also be included in the research design.

Several excellent study designs exist for this purpose and these consist of differing levels of complexity. Theoverall approach could begin with an ecologic or correlational level study, in which case the geographic area ofinterest would be defined first. As an example, this might include the entire geographic area previouslydelineated as the Central Florida Phosphate Mining District, or be more focused, including only those areas ofactive and historical phosphogypsum disposal. Having outlined the area of study, the population within thisgeographic area can now be defined with respect to total count, characteristics and proximity to phosphogypsumdisposal. This portion of the research may also identify the need to adjust the geographic limits of the study areato, let’s say, census or zip code delineations to accommodate the availability of population and chronic diseasedata. Chronic disease data in the form of the radiogenic cancers previously noted could be obtained from theDHRS, Florida Cancer Data Systems office in Miami for any pre-defined time period beginning about 1982forward. Likewise, health data referencing other disease endpoints could be obtained from the DHRS office ofVital Statistics in Jacksonville. These data could then be evaluated to determine the geographic distribution ofincident cases, case rates and standardized incident ratios when compared to some pre-defined referencepopulation. Of particular interest would be the proximity of cases to phosphogypsum disposal areas and ifstatistically significant space/time clustering is found.

A variation on this design was recently employed by the writer to study the occurrence of acute leukemias inadults and children in Florida on a county-by-county basis for the period of 1982-92. In addition to determiningthe occurrence of statistically significant ALL and AML incidence rates, a portion of this work also evaluatedthe potential for space/time clustering of leukemia cases and associations with selected environmental variables.One facet of this research included a regression and correlation analysis of leukemia incidence rates with

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radiologic data from the DHRS mandatory radon measurement program in conjunction with the FIPR LandBased Radon Study conducted in 1987. While aimed primarily at the occurrence of acute leukemias, the resultsof this work also identified a strong statistically significant correlation (r=0.78, p = < 0.001) for the FIPR andthe DHRS indoor radon data sets. These findings suggest that the 1987 FIPR study provided a veryrepresentative picture of radon occurrences throughout the state. This is rather remarkable given the differencein the size of both data sets ( FlPR-n=3500, DHRS-n= 18000). A statistically significant correlation was alsofound for indoor radon and radon in soil (r=0.70, p= <0.001), radon in soil and uranium in soil (r=0.54,p=0.00l), indoor radon and uranium in soil (r=0.41, p= <0.001), radon in soil and indoor gamma levels(r=0.29, p= <0.05), and uranium in soil with gross alpha activity in groundwater (r=-.32, p= <0.01). Aweak to moderate statistically significant correlation for the acute leukemias was also found but this was limitedto gross alpha activity in groundwater only. More definitive follow up studies are planned. The point here isthat large existing data sets can be creatively applied to a variety of research objectives.

Depending on the results of work at this level a decision can be made to end the research effort at this point orgo on to more definitive studies. More definitive studies would typically include a determination of toxicantexposure levels in air, soil or water in the hope that some dose response effect could be identified in associationwith cancer rate excesses. These studies might also focus on specific population subgroups based on thegeographic occurrence of cases and case rate excesses. Such studies could employ rigorous case-control andcohort epidemiologic designs aimed at a clearer definition of environmental exposures and disease endpoints.Factors related to exposure confounding and effect modification can also be included in these study designs. Akey element in the design and execution of these studies is the need to include sound data collection andstatistical analysis methods. While the aim is to identify statistically significant exposure relationships anddisease rate excesses, it is also important to elucidate the range of uncertainty and to establish the statisticalpower of these findings. This kind of approach provides a strong foundation for intervention (if required) andfuture research efforts.

In addition to employing research methods in environmental epidemiology, a parallel effort should be advancedin the area of health risk analysis. In doing so it is possible to partition the identified health risk into itscomponent parts employing both deterministic and probabilistic risk analysis methods. Such an approachprovides an opportunity to test both analytical methods against the results of the epidemiologic study. Moreover,applying the probabilistic risk analysis methodology provides an opportunity to “see” the distribution of risk anduncertainty for each of the component factors. This is an extremely powerful quantitative approach and it can bereadily facilitated with Monte Carlo Simulation and other probabilistic methods. Computer models designed forthis purpose are now in general use at the state and national level. It must also be emphasized that the overalldesign of the research approach discussed herein should proceed from a multi-discipline base bringing togetherexpertise in public health, medicine and the environmental sciences. This kind of approach will foster a morethorough and applicable end product that the public will find easier to embrace and that industry and theregulatory community will find more inherently sound for decision-making purposes.

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NORM RISK ASSESSMENTTHE WESTERN CANADIAN NORM GUIDELlNES

BY

DENNIS NOVITSKYWESTERN CANADIAN COMMITTEE ON NATURALLY OCCURRING RADIOACTIVE MATERIALS

* * * * * * * *

Author: Dennis Novitsky, Western Canadian Committee on Naturally Occurring Radioactive Materials(NORM).

Mr. Novitsky was the chairman of the Western Canadian NORM Committee that developed environmentalradioactivity guidelines for industry and government. He is currently a private consultant, but has spent about adecade with the Alberta government working with radiation issues. Among Mr. Novitsky’s career highlights isconsulting work with the Japanese government on environmental radiation contamination concerns andadministering a province-wide radiation protection program for workers, the public and the environment inCanada.

Mr. Novitsky earned a Bachelor’s degree in Physics from the University of Winnipeg, and an MBA from theUniversity of Calgary. He also received a Diploma of Technology in Nuclear Medicine from the BritishColumbia Institute of Technology.

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Introduction

The issue of Naturally Occurring Radioactive Material, or NORM, has been of increasing concern togovernment and industry in western Canada for well over 10 years. A Committee, the "Western CanadianCommittee on Naturally Occumng Radioactive Matenal (NORM)", has developed a guideline that is unique inits philosophical approach to NORM.

In Canada, NORM falls under the jurisdiction of the Provinces and the Territories. This has led to both gapsand overlaps within each province and to inconsistency between all provinces and territories in theadministration of NORM Canada-wide.

In 1990, as head of the the Province of Alberta’s radiation protection program, I approached the Alberta basedfertilizer and petroleum industries, to propose the formation of a bi-partite government/industry NORMCommittee.

Industry representatives recommended that the Committee mandate be expanded to other provinces. As well,having recognized that each province had its own unique set of NORM concerns, I approached the otherwestern Canadian provinces to participate in the Committee’s work.

Due to the state of flux present in the development of NORM regulations, Western Canadian governmentregulators supported the option of NORM guidelines development rather than pursue the traditional regulationdevelopment approach. Our industry colleagues on the Committee also supported this approach.

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On October 8, 1991 representatives from the fertilizer manufacturing and petroleum industries, met with severalAlberta government agencies and representatives from the provinces of British Columbia and Saskatchewan todiscuss the establishment of a western Canadian NORM committee. A complement of 15 met and establishedthe Terms of Reference for this committee. From this first meeting the "Western Canadian Committee onNaturally Occurring Radioactive Materials (NORM)", was officially formed and development of NORMGuidelines commenced.

The Norm Problem in Canada

As the acronym NORM implies, Naturally Occurring Radioactive Material contributes to the terrestialbackground radiation environment. It only creates a radiation protection problem whenever the radioactivecomponent of a material, is concentrated through some human activity.

NORM accumulates and concentrates in a variety of industry processes creating possible radiation exposurerisks to workers and the public. Industries in Canada with the potential for NORM problems include;

Fertilizer Manufacturing and other Mineral Extraction IndustriesIn the Province of Alberta’s fertilizer manufacturing industry, over 40 million tonnes of NORMcontaminated phosphogypsum have been stockpiled in four large stacks throughout the province.Petroleum Industries (oil and gas)Accumulation of NORM contaminated scale occurs in pipes, filters and other associated equipment bothup and downstream.Coal Fired Power GenerationCombustion of NORM contaminated coal in power generating stations, creates NORM contaminated flyash emissions.Pulp and Paper MillsLarge volumes of airborne low level NORM contaminated fly ash could deposit and contaminate thesurrounding countryside.Underground Mining OperationsOperations involved with the mining of non-radioactive materials where low levels of NORM are foundin the mined ore material.Other Underground Commercial/Industrial ActivitiesAny industrial activity involving the use of underground caverns, tunnels, vaults and large undergroundconduits.Water Treatment FacilitiesThe possible extraction of mineral impurities from water containing low levels of NORM.

The Western Canadian NORM Committee

An Alberta intiative, the “Western Canadian Committee on Naturally Occurring Radioactive Material(NORM)” was formed in October 1991. The Committee’s Mission Statement best describes the philosophicalapproach taken its adoption of NORM guideline standards.

MISSION STATEMENT OF THE WESTERN CANADIAN NORM COMMITTEE“Develop guidelines for the control of N.O.R.M. designed to ensure the same degree of protectionfor all workers and members of the general public, as those standards which have beeninternationally accepted”

The Committee’s Main Objective best describes both the methods and the holistic philosophy taken to overalldevelopment of the NORM guidelines.

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MAIN OBJECTIVE OF THE WESTERN CANADIAN NORM COMMITTEE“Development of a set of guidelines around; Classification of N.O.R.M., Worker Protection,Transportation, Waste Management and an Overview (What is N.O.R.M./Where is it found).”

The primary goal of industry representatives on the Committee has been to develop a consensus NORMguideline to serve as a reference for the development of Industry Codes of Practice while governmentrepresentatives had a goal of developing a concensus set of NORM standards to expedite the development ofconsistent interpretation criteria for the numerous provincial government agencies with some form of NORMjurisdiction.

As a whole, the Committee would like to see the Western Canadian Guideline, evolve into a National one. Anational Guideline can greatly enhance the development of consistency in the handling of NORM-relatedactivities, throughout Canada.

The Western Canadian NORM Guidelines

Overview;This guideline is by intent, a reference for two specific industries affected by NORM; petroleum producers andfertilizer manufacturers. We divided the guideline into three parts to provide appropriate information, tailored tothree distinct groups of readers:

Part I, For The General Reader, provides information to senior managers and administrators who may need toknow what NORM is, what responsibilities their company has in managing possible NORM problems, and whattheir budgetary implications for managing NORM may be. Part I provides general background information.

Part II, Technical Reference Manual, provides more detailed technical information to persons who haveresponsibility for preparing detailed plans for handling NORM. These persons are technical specialists such asEngineers, Occupational Hygienists and other Safety Professional who may have no direct experience in dealingwith radioactive material. Part II provides specific information on;

The NORM Standards-Basis and Criteria,Detection, Assessment and Monitoring of NORMProtection of Workers Exposed to NORMTransportation GuideEnvironmental Protection and Waste Management

Part III, Operational Guidelines, provides more specific information to worksite foremen and line supervisorswho, upon encountering NORM problems, must then make decisions on what precautions to take. Industryspecific information has been prepared for this group of readers. Part III has sections on;

NORM Operational Guidelines: IntroductionNORM and the Upstream Oil And Gas IndustryNORM Management in the Phosphate Fertilizer Industry

The Appendix includes a glossary of radiation terminology, a listing of radiation monitoring instrumentmanufacturers, radiation unit conversion factors, examples of NORM field survey and assessment forms and alisting of Radiological Laboratories and NORM Consultants.

The guidelines have been designed to allow for separation of parts I, II and III into stand-alone references. Thisformat allows subsequent expansion of Part III of the document, to include other industries as NORM becomesan identified concern to that industry sector.

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NORM Standards and Criteria;The Committee chose to establish NORM guideline standards by adopting the latest internationally recognizedstandards whenever feasible. A corollary consideration was to ensure that any adopted standard was identical toexisting federal regulation or planned amendments, or by reciprocity with other government agencies, deemedequivalent to those same regulations as administered by the Atomic Energy Control Board in their administrationof nuclear fuel cycle radioactive materials.

Above all else, the standards had to be recognized as scientifically sound and universally acceptable by nature ofthe involved international standard setting organizations and world renowned scientific experts involved withtheir development. The Committee wanted the guidelines to be as universally acceptable as possible given theincreasingly global nature of business today. As a result, the standards adopted by the Western Canada NORMCommittee were those developed by the International Commission on Radiological Protection (ICRP), theInternational Atomic Energy Agency (IAEA) and when compatible, Canadian national standards promulgated bythe Atomic Energy Control Board (AECB) and Health Canada.

Several issues were encountered and resolved by the Committee’s Standards Review Working Group including;

De minimus or Below Regulatory Concern (BRC) QuantitiesConfusion exists in the radiation protection community as to the criteria to establish De Minimusquantities for radioactive material versus those for Below Regulatory Concern. From a scientificperspective, a De Minimus quantity is derived by calculation based on an acceptable level of riskassumed by individuals (personal risk) or by society (collective risk) using risk based models. On theother hand, a BRC quantity, in addition to the scientific criteria, also incorporates other non-scientificsocietal concerns (eg. political) to establish an exempt quantity therefore, BRC quantities are almostalways greater than the equivalent De Minimus ones. Since the Committee’s overall objective was toadopt only scientifically based standards, the two quantities were viewed as essentially equivalent.

The Committee chose to use the IAEA set of Exempt Quantities and Concentrations since these aremore likely to reflect only the scientific criteria for their development

Exempt Concentrations and Exempt Quantities LimitsNORM can be either a diffuse source extending over a large volume or area or a discrete one. TheExempt Quantity standard is meaningless when assessing the risk associated with a diffuse source suchas a phosphogysum stack. The Committee recognized that two sets of limits had to be incorporated intoits De Minimus standards in order to address this difficulty.

RadonRadon has generated considerable controversy due to the lack of international consensus on itsradiological risk factors. Conflicting studies have resulted in conflicting interpretations of the inhalationrisk from radon gas and its radioactive progeny. As a result, Canada has a different interpretation ofradon risk than does the United States. Canada’s current recommended standard for residential radonexposure is based on a risk vs. benefit analysis conducted by a federal/provincial working group in thelate 1970s using radon house measurements obtained from a cross-Canada radon survey as source data.In this analysis, the relative costs per cancer averted was factored into the calculations. In the early199Os, a Health Canada funded epidemiological study in the city of Winnipeg, failed to show anassociation between radon exposure and an increased risk of cancer. Winnipeg has the highest averageresidential radon gas concentration measurements of all major Canadian cities.

This led our Committee to select the Canadian standard of 800 Bq/m3 over the recent 1994 ICRP 68recommended values of 200 to 600 Bq/m3. The Committee simply did not see research results that weresufficiently compelling to warrant a change. The Canadian standard has remained unchanged for similarreasons.

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The U.S. EPA standard was not considered.

Occupational Exposure LevelsTo support the implementation of the ALARA Principle, the Committee developed two exposurecategories within the Occupational Exposure Level; NORM-CONTAMINATED and RADIOACTIVE.(see attached figure)

As with many other aspects of NORM, the NORM-contaminated category was defined by default to bethe region of exposure which exceeded public exposure levels but failed to reach exposure levelssufficient to classify a worker to “Radiation Worker”.

In the “grey area” of NORM-contaminated, there is sufficient NORM material or radiation exposurepresent in the workplace such that ALARA is the dominant objective;

. Area monitoring should be performed on a regular basis (at least annually) and,

. Workers with the potential to exceed the public dose limit of 1 mSv/y are required toparticipate in a personal radiation dosimetry program.

NORM ClassificationThe NORM Classification scheme then falls within the Occupational Exposure Level categories. PublicExposure Levels can have only De minimus NORM quantities. The NORM-contaminated category ofOccupational Exposure Levels can only have NORM-contaminated quantities of NORM (exceeding Deminimus but less than Radioactive). Finally, the Radioactive Exposure category of OccupationalExposure Levels have NORM quantities in excess of the traditional Radioactive Possession limitsregulated by federal government agencies.

Issues Summary. De minimus risk values were adopted which provided the primary criterion for specifying

exposure levels.. Two Occupational Exposure Level categories were defined to account for the gap between a

Radiation Worker exposures and Public exposures.. Exposure Levels in turn provide the primary criterion to further develop NORM Material

Classifications within the Exposure Levels. This provides for a consistent and comprehensiveframework for the development of the balance of the guidelines. It is toward the NORM-contaminated Exposure Category for Occupational Exposure (the grey area) where the NORMGuidelines are directed.

Summary

This guideline development process represents a new way for government and industry to solve problems. Byinvolving all affected stakeholders in this consensus building process, an effective and practical NORMGuideline has been produced. As a guideline, rapid updates and revisions can be made which affords affectedindustry groups the opportunity to obtain current information.

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Discrete NORM Sources (Core sample/tilter sample/contaminated pump/)

External (Direct Exposure)

Radg hlterlsily wJv/hr) Surface Contama CBS/cm*)

Total Source Activity (Bq)

Internal (ALI)

Radon @q/m31 Radon Progeny Material Cone z% Total Sonrce Activity (Bq)

Discrete NORM Sources

DE MINIMUS NORM LIMITS OVERVlEW

Diffuse NORM Sources (P-Gyp Stacks/Ground Contamn/Air Contam’/)

I

External (Direct Expsonre)

Rab Intensity (pSv/hr) Surface Contam’ (Bqkm’)

Internal (ALI)

hrhale or hmest Radon Cont. (Bq/m3) Radon Progeny (WL) Material Cone (Bq/g) - Env’l Pathways (ALI) - Biochermcaf Pathways

DE MINIMUS NORM LIMITS LIMITS

External Exposure Internal Exposure (ALI)Extemal (Direct)

Rad’ hrtensity 0.5 pSv/hr Radon 1.50 Bq/m3 Surface Conk& 1 .O Bq/cn+ Radon Progeny 0.02 WL

Discrete Source Exempt Quantities (IAEA) Radioisotope Exempt Quantity (Bq) U(natnral) 1,000 Ra-226 10,000 Th(natnra1) 1,000

Pb-210 10,000

Diffuse NORM Sources

External Exposure

Rad-^ Intensity 0.5 $&4hr Snrf, Contam’ 1 .O Bqkm’

Internal Exposure (ALL)

Radon 150 Bq/m3 Radon Progeny 0.10 WL

Extended Source Exempt Concentrations (IAEA) Radioisotope Exempt Cow (Bq/g) U(natura1) 1 Ra-226 IO Th(natnra1) 1

Pb-2 10 10

NORM OCCTJPATIONAL EXPOSURE LEVELS

OCCUPATIONAL EXPOSURE LEVELS

RADIOACTIVE

NORM-CONTAMINATED

PUBLIC EXPOSURE LEVELS

DE MINMUS

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ANALYSIS OF RISK ASSESSMENT FOR USE OF WASTE PRODUCT PGIN BOTH AGRICULTURE AND ROAD CONSTRUCTION

BY

TONY JAMES, Ph.DACJ & ASSOCIATES

RICHLAND, WA

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Presenter: Anthony C. James, ACJ & Associates.

Dr. James has recently become an independent consultant after holding the position of Associate Professor in theCollege of Pharmacy at Washington State University. Prior to this Dr. James was the Chief Scientist in theOccupational and Environmental Health Protection Section of the Health Physics Department at Battelle, PacificNorthwest Laboratories. At Battelle, his primary research interest was in the development and application ofdosimetry of body tissues in humans and experimental animals, in order to address issues involved in settingpractical standards for radiological protection, and in relating cancer risks to environmental conditions ofexposure. Before joining Battelle in 1988, Dr. James had 17 years of research experience, much of it relating toradon, at the National Radiological Protection Board, Chilton, United Kingdom.

Dr. James has a B.Sc. in physics from University College in London and received the Ph.D. degree from theRoyal Free Hospital School of Medicine in London in 1969.

* * * * * * * *

Paper not available. The following is a transcription from video of Dr. James’ presentation at the Forum.

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I would just like to make one or two observations. The main one is that I am now in the interesting position ofworking for EPA as one of my consulting jobs, as one of a very large team which is putting together a criteriadocument, very much like the background information document. The criteria would be criteria to decidewhether or not the standard for exposure to particulate materials in the environment should be revised, the so-called PM-10 standard. So I’m working for the National Center for Environmental Assessments in ResearchTriangle Park. Next week I’m going to the second public review process which is a very stringent two dayevent. So I have got a lot of respect for the effort that goes into putting together these EPA documents.Essentially you can’t please both sides at the same time, but what they are trying to do with the PM-10document is get the science right. I think they have largely done that with the background informationdocument, but you do have some philosophical points that you can take exception to, such as using the scenarioof building a house on a disused roadbed is a realistic way of deciding if that is an unacceptable hazard. Theseare philosophical points. I don’t think you can criticize the science too much. It’s just whether or not thatstandard should be applied in the first place. The other point that you can debate is the level of risk that EPAhas set as the pivotal index of whether a practice is acceptable or not. Three times ten to the minus four is avery low risk. Now I have not actually produced my paper and I apologize for that, but what I will promise to

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do is put things into perspective. I have been working with lawyers too on several cases and lawyers are verygood at putting things into perspective which I think you want me to do. I do have a presentation, for example,comparing the risk of so many hours at age 70 is equivalent to in rems/year. So I will take on a duty to try andtailor that specifically to the dose rates that EPA is setting as the limiting factors in deciding on the acceptabilityof PG.

The average background for someone in the United States is somewhere between 1 mSv/year and 2 mSv/year.Now there are 100 mrem in 1 mSv so the general population is exposed to 100 to 200 mrem/year of backgroundradiation. Now if you are living somewhere like Colorado, which is a fairly healthy place to live, thebackground could be 3 times higher than that. Now EPA is setting unacceptable doses in the order of 70mrem/year. In other words, it is roughly doubling, or of the same order of magnitude as, background. That isthe criterion that they are applying to ban the use of PG in road making in relation to potential doses and risksfrom a reclaimer living on a road. We’re talking very much down at the background level. I would be verysurprised if any epidemiological study would have the power to even hint at finding any effect at that sort ofdose rate. You only stand a chance when you go to well identified populations that are exposed to pretty highlevels. 3 x 10-4 is a vanishingly small risk for any standard. If you can actually see it then someone is out byseveral orders of magnitude in their risk estimate.

As far as agriculture, one of the two limiting scenarios that concern, the critical issue I think is establishingwhat usage rates, what application rates on agricultural land are realistic. I think that if that can be establishedthen it should be possible to convince the EPA that use of PG in agriculture poses negligible risk. As far asroad construction, I think they should change their philosophy in terms of what criterion they set to judgeacceptability.

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-From video, transcript of questions and answers of Risk Panel discussion and conclusions:

POLICY PANEL QUESTIONS TO RISK SPEAKERS

POLICY PANEL DISCUSSION AND CONCLUSIONS ABOUT THE PROPOSED FIPR POLICYBASED ON WHAT’S BEEN HEARD

OHANIAN: Now before I turn to our policy panel with some questions I want to pose to them, are there anyadditional points that any of the speakers, either from this morning or afternoon, want to make, amplify onanything they have said before? I know Chuck Roessler wants to make a point.

ROESSLER: A question came up regarding whether the EPA had issued a permit for special uses with regardto road construction. The answer is no, but if we expand that to include agricultural uses, yes our Phase IIstudy is being carried out under a permit through EPA to use PG. In the middle of our work we got caught bythe rule and we did successfully get a permit to continue.

KENDRON: How much did you use?

ROESSLER: Jack?

JACK RECHCIGL: We got by with under 700 lbs.

OHANIAN: We have about 45 minutes to talk about a number of things and get the panel’s reaction on bothwhat was presented today, as well as the proposed FIPR Statement which you have in front of you, I believe.But let me first pose four questions that came to my mind. The first one is, are there clear-cut conclusionsregarding phosphogypsum utilization based on what you heard today? If yes, which ones? If no, what elseneeds to be done now? Based on what you have heard today, is the proposed FIPR Position Statement realisticand what additional information would be necessary if it is not? And fourth, where should we go from herewith all the information that we now have at hand? So now I’ll let anybody who wants to take a crack at one ormore of those questions.

ZAMANI: . .question of Dr. James or Dr. Roessler, on the level of radiation associated with the material usedin today’s road construction and how does it compare with the use of phosphogypsum, and what the EPA’sposition is on it?

ROESSLER: If we are talking about phosphogypsum from Central Florida, around 20-30, 25 pCi/g, and weare comparing that to sand and clay and other gravels and aggregate, usually these other materials are going tobe down around 1 or 2 pCi/g. On the other hand, if you are using various slags as a course aggregate, youcould have concentrations comparable to the phosphogypsum but with lower emanation coefficients. Certaintypes of granite rock and certain gravels, on the other hand, could be starting at 1 pCi/g and going up to, Isuppose, 5 or 10, but I don’t have anything more specific than that, other than, generally the materials arelower, and the ones I have encountered are lower in activity, but there are exceptions.

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GARRITY: This is not a question or answer to your questions, but I did have a question of Dr. Novitsky aboutsome of his work, I was wondering if you could go back over the comparison of 150 vs. 800 standard and tryto put that in terms of how that would correlate to U.S. standards.

NOVITSKY: O.K., the 150 Bq/cubic meter is the S.I. equivalent to your 4 pCi/liter; is the same thing. The800 Bq/cubic meter, Canadian standard was developed as a result of a cross Canada-Radon Survey done in thelate 1970’s plus a working group which was formed between the Provinces and the Federal government toaddress, not only the health risk associated with radon, but the economic factors in terms of how many dollarsper cancer averted is feasible. So the 800 Bq/cubic meter was basically a distilled quantity that came out of theanalysis. Does that help?

COLEMAN: Could you give an equivalency for me?

NOVITSKY: The 800 Bq/cubic meter is equivalent to 22 pCi/liter, so 5 times.

YOUNG: Further following up on that, is one a mitigation level and one an action level?

NOVITSKY: That’s right.

YOUNG: Maybe you could explain the distinction there.

NOVITISKY: Yes, the action level would be for a home owner, if they measure a quantity above 800, theywould need to mitigate to below 800, and the question is how far below 800 should you go. It isrecommended, that is why it is not quoted in the guidelines, that you should mitigate, if it is economicallyfeasible, to 150.

GARRITY: Maybe I should try to rephrase this in another way. Given the data that we have from CentralFlorida on levels of radium in phosphogypsum, if you had those levels in Canada, how would they beregulated?

NOVITSKY: Well, I should make a comment first of all, we do not have a federal equivalent set of regulationsthat you have here with EPA, so each province is on its own. That’s another reason why we came up withguidelines, because it was a way to sort of harmonize a disjointed regulatory framework. Basically, all I cansay in terms of regulations, is we go by what’s in the guideline because there is no formal regulation. As far asI am concerned, it is the table I presented in terms of the de minimus limits, because those de minimus limitswere derived in the I.A.E.A. Standard and called exempt quantities. Those quantities were generated throughscenario exposure analysis as to what kind of resulting dose would result, and 10 µSv dose to the individualover a year was the criteria to establish the exempt quantity. This could be considered a de minimus.

GARRITY: So do you think the levels in Central Florida would fall in the de minimus region?

NOVITSKY: Pretty well, 10 Bq/gram or 270 pCi/gram, according to the standard.

GARRITY: 10 Times higher?

NOVITSKY: 10 times.

YOUNG: I hate to dominate the discussion here, but as a policy maker who doesn’t have the technicalbackground and understanding that most of this group does, I am most intrigued by the assumptions that EPAhas made in developing its rules that have resulted in this prohibition, even for significant research projects. Ihear that there certainly is reason to question some of those assumptions. The assumption about the applicationrates, which in some instances might be that high, but, as was suggested best management practices or just

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limits could easily address that concern. The assumption about the lack of shielding, because we’re assumingthere won’t be floors in those houses, which will have a mitigating affect; assumptions about dose levels,what’s really an acceptable dose level. And then the biggest one, the assumption that I have the hardest timedealing with is this assumption that we’re going to allow houses to be built on roads. Which, again, seems tome easy to remedy, through a public policy which simply prohibits the building of houses on roads, even oldroad beds. And there are ways to deal with that. I guess my question to this group is how can we effectivelychallenge those assumptions? Because I don’t think there is a lot of dispute about the science. But its theassumptions that are going to get us into trouble when we go to the public and try to deal with these issues interms of public policies that make sense to lay people like myself. It seems to me that is where we need tobegin. I’m not convinced there needs to be a lot more technical research, although, certainly we need tocontinue to refine research. But with all the research we will never get to agreement unless we have someunderstanding at the outset as to what those assumptions are, what the acceptable dose levels are, and fromthere we can reach the standards.

WENZEL: I certainly agree with those remarks. I think the journalist comes out in me to a degree though inthat, if these are the assumptions, why is EPA to a degree being what could be called just out-and-outunrealistic about this? If these are the assumptions, I would think that we are living in a policy making time inthe United States where if the economic benefit is high and the health risk assessment is low, then therecertainly should be, within the policy realm, a good chance to get the EPA to take another look and to takeanother look at the research which exists. What I’m not hearing is the EPA’s side of things. I think that wouldhave been very valuable to this conference. If EPA couldn’t have represented their side, at least someone whocould have interpreted the EPA side. So, with that, I am wondering why EPA is basically being stoneheaded asthey apparently are, because I certainly agree with these assumptions to where, when there is a huge economicbenefit, and especially where we can reduce transportation costs in a state like Florida that will have hugetransportation shortfalls for funding. We certainly need an alternative.

OHANIAN: Very good point, Rod. As I explained our frustration at the beginning, EPA for legal reasons,wasn’t willing to do that. I don’t know, Tony, but since you’ve been working with EPA, maybe you couldshed some light on that point.

JAMES: No.

OHANIAN: Does anyone else want to comment on this, any of the speakers or the panelists here, on what Rodbrought up.

GLASSMAN: I’d like to pick up where Rod left off talking about transportation shortfalls. The groups Irepresent are the Florida Metropolitan Planning Organizations. They represent the expenditures on federal andstate funding within the urbanized areas in Florida. By no means is that the only organization interested inreducing the cost of transportation. Other groups, particularly the Florida Association of County Engineers andRoadway Superintendents, which is a national organization, not only co-founded in Florida, its also locatednationwide. In your policy statement I think what’s interesting is you note that the PG perceived environmentaland public health risk is misplaced. I think you would probably also want to say the risk and the issue itself isnot really known by that many folks as well. Although I’m involved in the transportation community, this isone option that should probably be surfaced with other organizations and they too should become a party to thisdiscussion and participate in a dialog on it as far as a remedy. And I’d hope you’d advance it with those typesof organizations so that they can participate.

OHANIAN: What particular organizations?

GLASSMAN: I’d look at the Florida Association of County Engineers and Roadway Superintendents forstarters. They’re a subset of the Florida Association of Counties. If there’s an issue there on a statewide basis,I think they could advance that issue. The MPO’s of to the state, which deal more with the urbanized areas of

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the state are another organization to look at. But the discussion I heard today, particularly from Polk County, isthat this might be a very good option for the county road system. The county road system in this state is under-funded. And typically the application of state and federal funds to the state highway system. Consistent withthat, I think DOT’s presentation has been that possibly this effort may not be as successful on high volumeinterstate and high volume arterial facilities, but the county road system might be an appropriate area to focus.

GARRITY: I had a comment on the position paper and I would like to say that I agree with everything thatCommissioner Young said. But in observing EPA these days, I see a different organization than might haveexisted 3, 4; or 5 years ago. I see an organization that is expressing interest in facilitated discussions andpartnerships in working with different groups. I think the mood of the position paper should be not so muchhitting them over the head and saying they are awfully stoneheaded and they had better do something or else. Itshould be more, “hey, we have all this evidence here indicating that we don’t see where the risk is, and whatwe want to have is a facilitated neutral type workshop maybe chaired by a good facilitator." It’s going toinvolve EPA, It’s going to involve industry, it’s going to involve state and local governments and is going toinvolve citizens groups sitting around the table coming up with some answers here. I just don’t see how theycan say no to that.

OHANIAN: Thank you. That is an excellent suggestion. We do actually have a facilitator. His name isLarry Gross and we can probably call on him.

O’HANRAHAN: I have this paper here. It’s about the benefits and costs that came out of Scientific American,Science and Medicine. It was published in Jan./Feb. 1995. And I’ll quote here, “U.S. EnvironmentalProtection Agency estimates that residential radon exposure causes approximately 14,000 lung cancer deathsannually, with an uncertainty rating of 7,000 to 30,000,” again uncertainty. “These deaths are presumed to bepreventable if indoor radon could be reduced to the concentration of outdoor air. Additionally, because themajority of,” this is very interesting, “because the majority of the 14,000 deaths are to smokers, smokingprevention and cessation would decrease these numbers." By the way, in my company smokers have a nicotinefit from the time they come in until they go out at the mandatory lunch period. And then they come back in towork and have a nicotine fit until they go home. No smoking allowed. “EPA has advocated the measurementof radon concentrations in residences,’ and by the way, the key word is that they are in residences, not out ofdoors, “and mitigation at the annual average is above 4 pCi/L, the action level.”

WIEGEL: I want to attempt to respond to Mr. Garrity. The reason we are here today is because six monthsago we tried to establish that dialogue with EPA and you see where we are now. We’re talking to ourselves. Ialso would like to ask the rhetorical question, how long before EPA gets its legal morass cleaned up? I mean,are we going to wait for 2 years, 5 years, 10 years and then go back to them again and ask for a conversationand be told “our lawyers say we cannot talk”. So I think your suggestion sounds great, but it is not going towork based on our experience.

COLEMAN: (To Garrity) Rick, I don’t want to seem like someone who is piling on, but as I mentioned you inthe hall, it was well over 6 months ago, it was more like 2 years ago, that we started to go through the head ofyour agency to have a direct dialogue. In fact to determine what the best expenditure of our funds for thepublic good on this issue might be, the best research that they would agree to at the same time, so that when wespent money it would be of value both to the EPA and to FIPR. We could not break through. We could notarrange a sit down to discuss that. Now you know that I believe in exactly the process that you proposed.Then we sat down 7 or 8 months ago and began this forum that you are now sitting in attempting to have boththe pros and the cons one after another speak, have all the experts in the room at the same time, give equalweight. But what we found is that they refuse to come or refuse to talk. And as a conservationist I’m reallyirate and upset that we cannot break through this barrier regardless of the good intent that may have initiated it.

OHANIAN: Are you going to talk on the same topic Larry?

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SMITH: No, I’ll tell you why.

OHANIAN: Can you hold on for just a minute?

SMITH: Sure.

OHANIAN: I’d like Rick to respond.

GARRITY: I hope I’m not being Pollyannish, but I have great empathy with the frustration that you areshowing from having tried to make this effort with EPA and them not responding. But still I would say that itwould be better worth our time and effort to try maybe once more to make some incisive strikes into the heartof the agency. As opposed to duking it out legally which can go on and on and on. Our agency is involvedright now with discussions directly between our secretary, secretary Weatherall, and Administrator Browner.And Ginger did get in there directly to see Carol. It was not easy, but she got in there. To have Floridadesignated a state to essentially take over EPA regulatory activity, but do it in a way that makes the best sensefor Florida to do things. To try to make common sense decisions based on different geographical areas of thestate. Ginger got a very positive response from Carol on that. Maybe its hard to get that philosophy to filterdown within the federal agency. But its there, and if we can grasp hold of it somehow, I think we can make itwork.

OHANIAN: Well perhaps you can help us with that issue.

YOUNG: Just adding to that. I think that Howard’s suggestion that we’ve really got to get a coalition ofinterests that goes beyond the industry or at least what is perceived to be basically an industry interest. Andalthough, at FIPR, we know the quality of the research and the objectivity of the research I think that there isstill a perception or there could be a perception that it is still industry supported and that its there to serve theindustry primarily. What we have got to do is get the public interest groups who understand the necessity andbenefits of either proceeding with research projects or going forward and actually utilizing this material inroadbeds. Its a huge economic issue, not just for the phosphate industry, but particularly for the tax payers ofthis state as it relates at least to road building. In my county alone, to give you an idea of the magnitude, weare dealing with a $300,000,000 transportation deficit at the county level. That is just the county road system.Now if road materials represented just 10% of that cost we’re talking about $30,000,000 to my county taxpayers. And of course overlay in all of that, the city cost, the state cost. We have got to partner here andwe’ve got to get our city government, our county government, our state government, and moreover our stateagencies. We need FDEP here with us on this issue. I have to believe that EPA is going to be a lot morereceptive to a sit down if FDEP is there as our partner at that table. So I think that we’ve really got to branchout now. And I think that the research is there to support that position and to make a very powerful andpersuasive argument to the public and to all those affected groups.

OHANIAN: Anything else on this same topic? Larry.

LARRY: You may interpret this to have some affect on what we’ve been talking about. In dealing withcontractors there is an old saying that they want a level playing field. And I think that is what we are talkingabout here. Translated that means that I’m going to be honest and you are going to be honest about the subjectat hand. To give you an example, in 1988 the state of Florida passed a rather aggressive bill requiring manystate agencies to involve themselves in recycling. There was a scenario that came forward then that has provento be very successful. It enticed the political, regulatory groups and such agencies as the Department ofTransportation. It’s by no accident that we were the first state to utilize ground tire rubber consistently in ourproduction programs. From what I’m seeing here and what I’m hearing, I’ll say it in a negative fashion and I’lltry to say it in a positive fashion. We have a disjointed effort. In a more positive since we are not coordinated.When we were finishing the ground tire rubber research the question of worker risk came forward. Now as anagency, the Florida DOT cannot, and neither can the counties or other agencies assume large liabilities that they

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don’t have to. We spent a quarter of a million dollars to do an air quality study with the ground tire rubber. Inorder to get the contractor to do that we had to indemnify him. So the stakes are big. And phosphogypsum isjust one of them. Take construction debris, take all the ashes that are on the ground in this country and youhave the same scenario. But I think one of the concerns that I see and it has been stated here, and I’m notgoing to be as negative. But from an engineering point of view we can do a lot. It’s no mystery to go out andassess the strength of a road and make some general predictions. But what I’m hearing is that there are noground rules on assessing risk. And that’s the bottom line. And only now in this state, and we have to giveDEP credit here, to move into that assessment arena. Now I want to make several suggestions. This state haslarge sums of money which we used to spend in over coming corrosion activities. Today we have gone beyondthat and when we do research in corrosion now we require the researcher through some very extensivemodeling to make some long term predictions. That is what is needed here. I don’t have the answer. Dr.James skirted that issue. But you need to be able, with some assurance, pinpoint down the road. And I thinkinitially your going to have to assume some risks. And Dr. Ohanian, I think the conclusions can be stated yes,from a technical point of view we probably know what we are doing. But we are stymied by the fact that wewill not, or I will not recommend for my agency to assume the risk. It is impossible for us to do that. As faras the position statement, it is kind of innocuous. All you are saying is take a second look. So I would have noproblems with that. Where we go from here, I think, and it was mentioned earlier, and what we are trying toforce in this state alone is when DEP starts some of their regulatory issues, we sit down as a technical groupand show them the engineering side. With the stroke of a pen EPA yielded the ashes coming out of the coalplants in this state to eventually be of no value to us. In our program alone we use 500,000,000 tons ofconcrete. We approach every utilization of waste as a positive direction. That enhanced our concrete. That’sthe program today by which we can put concrete in bridges, and with a great deal of assurance say that that’sgoing to last 75 years without corrosion problems. Twenty years ago that time frame was 15 years. So we canuse waste, and I think that needs to be a core of any action you take forward. You want to do it in a positiveway and you want to do it with economics. The economics have not been discussed in great detail. But in1975, when we started recycling asphalt, we did it because of the oil embargo. And if you ever get another oilembargo or any type of energy crisis you will find out what transportation is again. You know we’ve forgottenthose days. But you need a level playing field. I encourage you to try to work at the national level. We aretrying to work at the state level. I agree with the comment DEP is your transition to EPA. They will listen.They’ve got some good people. I admire those people. But we have to have a real target on liability or thiswhole thing comes to a halt. Thank you.

WENZEL: I’d like to follow up on the economics. I think that in trying to sell this to the mass media, and thatis where you will end up getting your largest audience, we can sit here in a room of 200 but as soon as you puta message out to the media 200,000; 2,000,000 start to quickly understand it. I think as best you can start tosell your story to the general public, the better chance you will have of catching the type of political andnational attention you will need to then, for a second look potentially, to be taken. Within the policy arena inD.C. and around the country today, I think what we’ve just heard at the county level is an important point.Three hundred million dollar shortfall for transportation? If ten percent of that could be saved, that’s$30,000,000 for a county to use, on what? On children. In handling the child crisis in our state instead ofspending the money on concrete and cement. And to me that’s a good sell. I think when you start to be able toproperly interpret what can be the real public benefit, and public benefit really isn’t cheaper roads. The publicbenefit is, we then take the money that we would have spent on roads and spend it on something like healthcareor something like children that is a human cause. I think when we start to capture mass media attention withthat type of analysis and interpretation you will go a long ways toward getting this on the public agenda. Onething I’ve heard today, I really hope the group can better articulate what is the risk assessment here. I don’tknow that I properly understand EPA’s 3 in 10,000. I know I would not go to the airport tomorrow and get ona jet plane if my chances of a crash were as high as 3 in 10,000. Airways are safer than that, etc. And I thinkthat what the risk assessment is needs to be properly interpreted and articulated and hopefully accuratelyarticulated. In dealing with mass media and trying to get your message across, there is a real error rate thatoccurs if you’re trying to build a campaign and yet any part of that campaign has error in it. That is whereyour environmental groups, your health groups, and your political groups will really take fast and quick

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exception. I think my best suggestion I can give you from my background would be to try to articulate what theissue is in terms of the human benefit and the human benefit as a side effect of what really would become theeconomic benefit which is certainly of an interest, too.

SAYLAK: I want to follow up on what Rod was saying, and possibly make a suggestion. I really and trulyagree with you that the media, the mass media would be a tremendous force in helping us start to moveforward, but some of us in this room remember reading papers frivolously written with cartoons asking fordirections to the road which lights up in the dark. In other words, it made fun of a situation and scared peoplefor the sake of, whatever. If we can get objectivity in the media, to counteract what they brought to thissituation, I think we would be further along. Now, my suggestion is, and with all of this risk aspect, there isone thing that I, and I guess it is because I come from a research community, that maybe selling hundreds andthousands and millions of tons of this stuff might have to move along, but for the life of me, why I can’t get a55 gallon drum off of Mobil Chemical Co. ‘s stockpiles so I can do research. My people do research on farmore radioactive material than this, to try to encapsulate it. Why I say this is if we can get off the dime and atleast get a concession to allow us to do research, then when comes time to make these convincing arguments weare not going to be doing it with data that dates back to 1983 like I have been showing. So I think we can go along way by being able to get back into the research arena again and at least present our results in terms ofcurrent results rather than something that’s over 12 years old.

JAMES: The EPA has conceded the point about being unrealistic to eliminate research, hasn’t it?

OHANIAN: No, not as far as we know. Mike?

LLOYD: EPA, in march of 1994, said that the research ruling was erroneous, it had to be changed, and thatthey would promptly issue a change. This is December of 1995. Now your promptly may be a little bitdifferent from theirs. They have told me in the last several months that this ruling would be issuedmomentarily. Well, I’m waiting.

OHANIAN: Richard, you have something?

COLEMAN: Yes, there are a couple of things, and I think I’ll take them in a reverse order, no, no I won’t.This really came from the audience, and let me go over this rather cautiously. Florida has, I used to think 600million tons of phosphogyp. We’re hearing 700 and everybody seems to be accepting 700 now, almost all ofwhich are in unlined stacks awaiting for proper closure. The major gut environmental issue concerning thesestacks is ground water contamination from process water and leachate from the existing unlined stacks.Opportunities for cost savings relating to maximizing efficient use of new expensive lined stacks or theopportunities for cost savings really come in the use of the new expensive lined stacks. If gyp could be used forother purposes, it appears likely it would come from current production at 30 million a year. It would be awonderful achievement to productively use 30 million tons a year, the amount of gyp that is currently produced,that’s a lot of product. If we achieve that goal, Florida will still have 700 million tons of phosphogypsum inunlined stacks awaiting for, or undergoing closure. Diversion of closure funds, which has been suggested forresearch, does not seem, in light of statements, to be an appropriate or reasonable source of funds. Othersources need to be identified. If someone wants to comment on that any where in here, I’ll be glad for them todo it. It is something that came from the audience.

ZAMANI: I think Phil (Coram), this morning, mentioned the financial responsibility in the requirement that isassociated with the closure of the gypstacks. This money is just a demonstration of their financial strength.This is not the amount of money that is put aside, that somebody could tap that money and use it towardsalternative use for gypsum. It is just a financial test that each company goes through, I just want to clarify thatpoint.

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COLEMAN: Something that I see coming out of the discussions here might be a revised version of the FloridaInstitute of Phosphate Research proposed position. And the more I hear coming from the speakers and theexperts and the audience, the more I think of a proposal that came to me here might be appropriate. And let meread it, Jack. “FIPR has concluded from its experimental studies of phosphogypsum and that of otherresearchers, that much of the official concern about phosphogypsum’s perceived environmental and public healthrisk is reasonably debatable.” I believe that actually, Mr. James used the term, ‘Reasonably debatable’. “Manyof the proposed uses of phosphogypsum appear to involve levels of risks which may have potential for mitigationusing currently available practices.” We have all been saying that. “Therefore, in light of the potential economicadvantages of proposed uses for phosphogypsum and the demonstrated environmental and economic costs instacking and monitoring phosphogypsum, the U.S. EPA should be strongly urged to re-evaluate its restrictions onphosphogypsum research.” What we have just been hearing. “Further upon completion of large scale researchand substantial appropriate peer review, EPA policy should be amended to appropriately reflect the scientificconsensus of the risk and mitigation of the storage and use of phosphogypsum.”

OHANIAN: Any comments on that.

YOUNG: In light of all of the comments that have been made, but particularly the one about the need toinvolve the public and get the public to support these efforts, I think that is a much preferred substitute policy. Iwas concerned in looking at this after several times, that the way that it was phrased might suggest that we weredismissing the concerns, and we certainly don’t want to give that message to the public. But I think that is verywell thought out. I would support that.

OHANIAN: Thank you. Any other comments on this? Does anyone have anything else?

LLOYD: As an action point. Ms. E. Ramona Trovato, head of the NESHAPs branch of EPA in Washingtonhas indicated a willingness to sit down and talk about this. It might be worthwhile to the panel to suggest thatthe board meet with her within some reasonable time or be able to say that she just won’t talk to you.

OHANIAN: Well Mike, as you recall, we did discuss that at the last board meeting and we agreed that wewould do something like that. So that is not an issue. Let me make a couple of comments and then I think weshould end. It is almost 5:00 and it’s been a long day. I hope you all come to the reception on the 22nd floorof the Capitol so that we can continue our discussions. It seems to me that we need to make a commitment tocontinue the discussion/dialogue. In fact I’ve asked the board members to stay over night so that we can meet at7:00 tomorrow morning with the staff and see where we will go from here. But also by the same token I hopethat, especially, not the board because they are already committed, but the others that we have invited willcommit themselves to working with us for the next couple of months to get to a specific point. We will create asummary of these deliberations; obviously there are eight or nine hours on the tv tape. We’ll do that with thehelp of Larry Gross. We’ll get that to everyone who was here probably within the next month. Certainly by themiddle of January and no later than that. I think that’s very important. With that I want to thank all of you forbeing here. I especially want to thank all the speakers this morning and this afternoon who came. They madeexcellent presentations. And I want to thank all the panelists at the table here for your time. I think it is veryimportant that we help both the state and the federal government, and especially all of the citizens in this state toresolve this health issue, and more importantly as some people have pointed out, a very important economicalissue as well. Again thank you and we’ll see you in about half an hour.

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Assessment of Doses and Risks from Uses of Waste ProductPhosphogypsum in Agriculture and Road Construction

Presented at the Phosphogypsum Fact-Finding Forum, Florida StateConference Center, Tallahassee, FL, December 7, 1995

Anthony C. James, Ph.D.

ACJ & Associates129 Patton St.

Richland, WA 99352-1618

BIOGRAPHIC SKETCH

Dr. James holds a B.Sc. in Physics and a Ph.D. in Radiation Biology, both from the University of London, England. Hisprincipal research and professional interest is in the development and application of radiation dosimetry of the respiratorytract and other body tissues in the human and in experimental animals, in order to address the issues involved in settingpractical standards for radiological protection, and in relating human cancer risks to environmental conditions of exposure.In September, 1995, Dr. James completed a one-year appointment as an Associate Professor in the College of Pharmacy,Washington State University Tri-Cities Campus, Richland, WA, together with part-time private consulting work. He isnow the Proprietor and Chief Consultant of ACJ & Associates, a company specializing in consultancy in the areas ofinternal radiation dosimetry, inhalation hazard assessment, and related scientific disciplines. Until December, 1994, Dr.James was a Chief Scientist in the Health Protection Department of the Life Sciences Center, Battelle NorthwestLaboratories, Richland. Before joining BattelIe in 1988, Dr. James had 17 years of research experience at the NationalRadiological Protection Board, United Kingdom, relating to radioactive aerosols (especially plutonium and radon progeny)and their dosimetry in humans and experimental animals. In the United States, he was a member of the National ResearchCouncil’s Scientific Panel which reported on “Comparative Dosimetry of Radon in Mines and Homes.” His internationalwork has included membership of two Task Groups of the International Commission on Radiological Protection (ICRP),reporting on: “Protection Against Radon-222 at Home and at Work“ (ICRP Publication 65, 1993); and a “HumanRespiratory Tract Model for Radiological Protection” (ICRP Publication 66, 1994). He is currently a correspondingmember of the ICRP Dose Calculations Task Group, and also a member of the U.S. Interagency Nuclear Safety ReviewPanel/Biomedical and Environmental Effects Subpanel (INSRP/BEES), which advises the Department of Energy, NationalAeronautics and Space Administration, and Department of Defense on the adequacy of safety assessments for spaceflightmissions involving reactors or radionuclide heat sources. He was recently appointed as a U.S. Delegated Expert on InternalDosimetry for the joint USNRC/Commission of the European Communities (CEC) study of “Uncertainties in RadiologicalConsequences.” Dr. James has been published over 100 articles in the scientific literature.

SELECTION FROM PUBLICATIONS

Group of Experts of the OECD Nuclear Energy Agency. 1983. “Dosimetry Aspects of Exposure to Radon and ThoronDaughter Products.” A. C. James, lead author and editor. Organization for Economic Cooperation and Development, Paris.

James, A. C. 1988. “Lung Dosimetry.” Pp. 259-309 in Radon and Its Decay Products in Indoor Air. W. W. Nazaroff andA. V. Nero, eds. John Wiley and Sons Inc., New York, NY.

Samet, J. M., R. E. Albert, J. D. Brain, R. A. Guilmette, P. K. Hopke, A. C. James, and D. G. Kaufman. 1991.“Comparative Dosimetry of Radon in Mines and Homes.” National Academy Press, Washington, DC.

James, A. C. 1992. “Dosimetry of Radon and Thoron Exposures: Implications for Risks from Indoor Exposure.” INIndoor Radon and Lung Cancer: Reality or Myth? F. T. Cross, ed. Pp 167-198. Battelle Press, Columbus, OH.

Bair, W. J., M. R. Bailey, F. T. Cross, R. G. Cuddihy, P. Gehr, A. C. James, J. R. Johnson, R. Masse, M. Roy, and W.Stahlhofen. 1994. International Commission on Radiological Protection (ICRP) Human Respiratory Tract Model forRadiological Protection. ICRP Publication 66. Ann. ICRP 24(1/4).

James, A. C., W. Stahlhofen, G. Rudolf, J. K. Briant, M. J. Egan, W. Nixon, and A. Birchall. 1994. Annexe D:“Deposition of Inhaled Particles.” In: International Commission on Radiological Protection (ICRP) Human RespiratoryTract Model for Radiological Protection. ICRP Publication 66. Ann. ICRP 24(1/4).

James, A. C., M. Roy, and A. Birchall. 1994. Annexe F: “Reference Values for Regional Deposition.” In: InternationalCommission on Radiological Protection (ICRP) Human Respiratory Tract Model for Radiological Protection. ICRPPublication 66. Ann. ICRP 24(1/4).

James, A. C., G. Akabani, A. Birchall, N. S. Jarvis, J. K. Briant, and J. S. Durham. 1994. Annexe H: “Absorbed Fractionsfor Alpha, Electron, and Beta Emissions.” In: International Commission on Radiological Protection (ICRP) HumanRespiratory Tract Model for Radiological Protection. ICRP Publication 66. Ann. ICRP 24( l/4).

INTRODUCTION

In 1992, the United States Environmental Protection Agency (EPA) issued the National EmissionStandards for Air Pollutants (NESHAP); National Emission Standards for Radon Emissions fromPhosphogypsum Stacks, 40 CFR Part 61, Federal Register, Vol. 57, No. 107, June 3, 1992. TheEPA’s NESHAP ruling was based on the Background Information Document (BID) on “PotentialUses of Phosphogypsum and Associated Risks,” published by the EPA two months earlier, in April,1992 (Conklin et al., 1992).

In the anticipation of small but finite risks to human health that might arise from the radionuclidecontent of phosphogypsum (PG), the 1992 NESHAP ruling (I) required the disposal of PG inmonitored stacks or mines; (ii) prohibited the use of PG for the purpose of road construction; (iii)prohibited the agricultural use of PG containing more than 10 pCi g-’ of 226Ra, and; (iv) limited thequantity of PG that could be used in any particular research and development project to 700 lb. Inresponse to a “Petition for Reconsideration,” submitted by The Fertilizer Institute (TFI) to theAdministrator on August 3, 1992, the EPA acknowledged in March, 1994, that the latter limitationshould be relaxed to allow the use of 3,500 lb of PG in research and development work. Thisdecision was occasioned by the discovery of an error in the BID, whereby EPA’s calculations hadin fact been performed for five drums of PG in a laboratory setting, rather than the “single drum”stated inadvertently in the BID. However, the EPA denied TFI’s petition for reconsideration of theruling that PG must be disposed of in monitored stacks or mines, and that it must not be used foragricultural or construction purposes without an appropriate reduction of the 22!Ra concentration.

In deciding whether or not PG (with an assumed “typical” 22!R a concentration of 26 pCi g-‘) couldbe used for agricultural or construction purposes without regulation , the EPA applied the criterionthat the estimated maximum additional lifetime risk to any individual who might be exposed toradiation by such practices should not exceed 3 x lo-“. The EPA considered several hypotheticalscenarios to define the maximum reasonable exposure (MRE) from agricultural and constructionuses of PG. For very heavy, loo-year-long agricultural application of PG as a source of nutrientsor as a soil conditioner, the resulting maximum individual risk (MIR) was calculated to be 1.8 x10-3. This estimated risk applied for a so-called “reclaimer,” who was assumed to have lived for 70years in a house built on redeveloped agricultural land. The corresponding MIR for use of PG inconstruction was calculated to be 9.3 x lo”, for a reclaimer who had lived for 70 years in a housebuilt on a disused road (with both a PG-concrete surface and road bed left intact).

TFI’s petition to the EPA’s Administrator was based on the findings of a preliminary review ofEPA’s final ruling and BID, which was carried out in July 1992 by SENES Consultants Ltd.(Richmond Hill, Ontario). SENES’s review indicated several factors in EPA’s exposureassumptions which may have led the Agency to overestimate the MRE of potentially exposedindividuals by an overall factor of approximately six for the application of PG to soil and the useof PG on roadbeds, and by a factor of forty for work with PG in a research and developmentlaboratory. If substantiated, such degrees of overestimation would seem to be sufficient justificationfor the EPA to reconsider its ruling.

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Accordingly, in September, 1993, the FIPR Board of Directors commissioned the Battelle NorthwestLaboratories (BNWL) of Richland, WA to perform an in-depth analysis of the accuracy of EPA’sexposure assumptions, calculational models, and resulting risk determinations. This study wasconducted by Dr. John R. Johnson, Chief Scientist of BNWL’s Health Protection Department, withassistance for computations and modeling by Dr. Richard J. Traub, Staff Scientist. The author(ACJ), in his capacity as an Associate Professor at Washington State University’s Tri-Cities, WAbranch campus served as a consultant to BNWL for this project.

At the time of this Forum, BNWL’s study and final report is not yet complete. However, based onthe available results of calculations, I will provide for discussion my personal view of the outcomeof the study. I will focus on the assessments of individual risks for the exposure scenarios that theEPA deemed to be critical in preventing the widespread use of PG in agriculture and construction.In these scenarios, two components of exposure were considered to be significant in terms of riskto health; (I) the additional gamma radiation to the occupants of a house built on PG-treated land,or that from a contaminated road bed under the house, and (ii) the additional exposure to radonprogeny that would occur inside such houses. Finally, I will attempt to put the calculated lifetimerisk of 3 x lOa (ie., EPA’s criterion for an “acceptable” risk), into some perspective in comparisonwith risks of premature death that are present in general, “everyday” living.

DOSES AND RISKS FROM AGRICULTURAL USES OF PG

The EPA evaluated seven scenarios in which PG might be used in agriculture. The exposurepathways estimated to produce the highest risk (i.e., increased external gamma radiation plusincreased inhalation of radon progeny) were for an individual living and working in a houseconstructed on land previously treated with PG. The range of application rates of PG, and the soilconditions considered, are shown in Table 1.

Scenarios 1 through 4, were assumed to represent the application of PG to add calcium and sulfurto soils deficient in these elements; 1 and 3 representing “average” and “maximum” biennialapplication rates, respectively, for a clay soil, and 2 and 4 the same application rates for sandy soil.The PG is mixed and diluted in the tilled layer of soil, but over time the initial 226Ra-in-soilconcentration increases with continued application, until equilibrium is reached with loss of PG andits constituent radionuclides (i.e., by plant uptake, leaching by infiltration of surface water, wind andwater erosion). The steady-state concentrations of 226 Ra that are calculated to be present in thetilled layer of soil, after 100 years of biennial application of PG at these rates, are also shown inTable 1. It is notable that the assumed “maximum” increment in the 226Ra soil concentration fromuse of PG to add soil nutrients (scenarios 1 through 4) is less than the value of about 1 pCi g-1 thatis present naturally in Florida soils. The corresponding “maximum” calculated increment in lifetimerisk is the sum of 3.2 x lOA from increased direct gamma irradiation, and 4.8 x lo4 from increasedindoor exposure to radon progeny, i.e., -8 x lOA. This is about a three times higher risk than thevalue that EPA considered “acceptable.”

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Table 1. EPA’s assumed rates at which PG might be applied to agricultural land, with the resulting incremental 226Ra concentration in soil after loo-year application of PG

containing 26 pCr * 226Ra per g, together with the estimated annual dose rates and/or incremental lifetime risks.

Parameter Exposure Scenario

1 2 3 4 5 6 7

Soil base Clay Sand

Initial application (kg/acre)

Biennial application (kg/acre)

Tillage Depth (cm)

Increase in 226Ra concentration in soil (pCi/g)

Clay Sand Clay Sand

N/A N/A N/A N/A 17,600 17,600 N/A

1,461 1,461 4,470 4,470 8,800 8,800 500 - 10,000 (2,622)

22 22 46 46 30 30 23

0.45 - 0.60 0.60 0.88 0.88 2.70 2.70 (29306) .

BID - Direct yamma

Annual dose rate (mrem/y)

7.6 7.6 12.0 12.0 35.0 35.0 (27.5)

Lifetime risk 2.1 x 2.1 x 3.2 x 3.2 x 1.0 x 1.0 x (7.7 x lo4 loa lOA lOA 10” 1o-3 10d)

BID - Indoor radon

Lifetime risk 1.8 x 1.8 x 4.8 x 4.8 x 8.4 x 8.4 x (7.0 x lOA lOA lo4 10”’ lOA lo4 10d)

The EPA assumes that scenarios 5 and 6 apply to the use of PG as sediment control, for soils that have been eroded and leached. Based on an example from California, it was assumed that the amount of PG initially applied is 8,000 kg/acre (17,600 lb/acre), followed by biennial application of 4,000 kg/acre (8,800 lb/acre) for 100 years. The resulting increase in the concentration of 226Ra (through the tillage depth) was calculated to be 2.7 pCi g-l, i.e., almost three times the natural 226Ra level in the soil. The corresponding calculated increment in lifetime risk was then the sum of 1 .O x 10” from increased direct gamma irradiation, and 8.4 x lOa from increased indoor exposure to radon progeny, i.e., - 1.8 x 10e3, which is about a six times higher risk than the value that EPA considered “acceptable.”

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The seventh scenario considered by the EPA was included to illustrate that the incremental doserates and/or lifetime risks are proportional to the product of the PG application rate and the 226Raconcentration. On this basis, the EPA ruled that it would be acceptable to use PG for agriculturalpurposes, provided that the 226Ra concentration did not exceed 10 pCi g-l. The values shown inparentheses in the right-hand column of Table 1 give the gamma dose rate and components oflifetime risk calculated for a median application rate (2,622 lb/acre, biennially) of PG containinga 226Ra concentration of 26 pCi g’ , which is typical of the PG produced in central Florida. Theresulting estimate of the increased lifetime risk was about 1.5 x 10m3, or slightly less than that forapplication scenarios 5 and 6.

Reassessment of Risks for a Land “Reclaimer” from Agricultural Use of PG

The scope of BNWL’s reassessment of doses and the associated risks from agricultural uses of wasteproduct PG is as follows.

l Assume EPA’s exposure scenarios for evaluating the maximum individual risk (MIR) to a so-called “reclaimer” from lifetime exposure in a home built on reclaimed agricultural land, i.e.,after 100-y application of PG containing 26 pCi g-’ of 226Ra and its radioactive progeny.

l Model the two critical exposure pathways;- direct gamma irradiation, and;- inhalation of radon progeny formed from radon that seeps into the indoor air.

l Assume EPA’s adopted risk factors (EPA, 1994), which are similar to those currentlyrecommended by International Commission on Radiological Protection (ICRP, 1993).

Direct gamma exposure

In calculating the direct gamma dose to the occupants of a home from a historical accumulation of226Ra-bearing PG in the soil under the home, the EPA assumed that the floor of the home providedno shielding, and that no imported backfill material had been used in the foundation structure.However, the most common type of home construction in central Florida is the so-called “slab-on-grade” construction, whereby a thickness of about 0.3 m (1 ft) of imported backfill material is laidinside the foundation walls. The house floor is then formed by a 0.1 m (4 inch) thickness ofconcrete laid on top of the backfill. Taking as an example EPA’s exposure scenarios 1 or 2 (fromTable l), the effect of introducing these layers of shielding material in reducing the direct gammadose rate to the occupants of a home built on reclaimed agricultural land is as follows. For 100-ybiennial application of 1,500 lb/acre of PG, and a tillage depth of 22 cm:

l the incremental 226Ra concentration in the surface soil is 0.6 pCi g-l; and,. EPA’s calculated incremental dose rate is 7.6 mrem y-l.

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The corresponding dose rates calculated by BNWL are:

l 6.0 mrem y-l - ignoring the shielding provided by the floor and backfill;l 2.4 mrem ye’ - allowing for the shielding provided by the 0.1-m thick concrete slab; and,. 0.1 mrem y-l - allowing for the additional shielding provided by a 0.3-m thick layer of imported

backfill.

It is seen that BNWL’s calculated value of the gamma dose rate in the absence of the shieldinglayers is somewhat lower than EPA’s (6.0 mrem y-l cf. 7.6 mrem y-l). This difference is due toEPA’s assumption that PG contains a higher proportion of the 23qh isotopic series of radionuclidesin relation to the 226Ra series than is actually the case. However, neglect of the shielding providedby the concrete slab and backfill material led to a much greater overestimate of the direct gammadose rate in EPA’s analysis; by a factor of almost eighty.

EPA based their ruling to prohibit the use of “undiluted” PG in agriculture on the assumption of themaximum individual risk (MIR) defined by exposure scenarios 5 or 6 (see Table 1). Using theEPA’s risk factor (3.83 x 10m7 per mrem) that is attributable for a lifetime (70 y) of whole bodygamma irradiation at the calculated dose rates, the resulting estimated increases in lifetime risk fromdirect gamma exposure in a home built on land that had received biennial PG applications of about9,000 lb/acre for 100 y (giving an incremental 226Ra concentration in soil of 2.7 pCi g -’ ), are asfollows:

l 10 in 10,000 (1 x 10”) estimated by EPA;l 8 in 10,000 (8 x lOA) estimated by BNWL for “no shielding” provided by the floor;l 3 in 10,000 (3 x 10”) estimated by BNWL for the shielding provided by a 0.l-cm thick concrete

slab; and,l <3 in 100,000 (<3 x 10m5) estimated by BNWL for shielding by both the concrete slab and

backfill material.

It is seen that, having taken account of the shielding provided by the “slab-on-grade” constructionof a typical central Florida home, the additional lifetime risk for a lifelong occupant contributed bydirect gamma irradiation is less than one-tenth of the 3 x lo4 value deemed by the EPA to be“acceptable.”

Indoor radon exposure

Realistic assessment of the build up of radon in a central Florida home built on soil contaminatedwith an elevated concentration of 226Ra requires the application of a quantitative model of theingress of radon through the floor-wall junctions of a slab-on-grade foundation. Such a model wasdescribed by Revzan et al. (1993). These authors used their model to calculate the variation in theradon entry rate caused by wide variations in each of the many physical parameters (e.g., soil, fill,and stem-wall permeabilities, and the widths of various gaps in the foundation through which soilgas flows under the positive pressure gradient that exists between soil gas and indoor air), and

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available pathways that affect radon entry. The details of the foundation structure that are included in the Revzan et al. model are shown in Figure 1.

Concrete

Block wall

0.028 m

Figure 1. Detail of floor and wall for Florida slab-on-grade house showing air gaps, backfill and native soil.

Source: Revzan et al. (1993).

Revzan et al. ‘s model calculates a “‘best estimate” of 2.3 Bq s-’ (62 pCi s-3 for the total rate of entry of radon into the indoor air of a slab-on-grade constructed home, assuming that the concentration of “free” radon in soil gas is 1 pCi g-l. However, on comparing their calculated values with experimental results in real homes, these authors concluded that the model tends to underestimate the actually observed entry rate of radon by a factor of two. Thus, to assess the effect on radon entry into indoor air of increasing the concentration of radon in soil gas, it is prudent to multiply by a factor of two the values given by the Revzan et al. model. I have done this to derive the radon exposure estimates given below.

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The concentration of radon in soil gas is determined by the product of the 226Ra concentration andthe so-called “emanation fraction” for radon gas, i.e., the fraction of the total number of radon atomsproduced inside the particles of soil (or PG) that are released into the soil gas spaces. Theemanation fraction is significantly less than unity. Rutherford et al. (1995) found that the value forFloridian PG is approximately 0.12. Assuming a “rounded” value of 0.15 for the emanation fraction(which is half the value of 0.3 assumed by the EPA in their calculations), together with twice theradon entry rate calculated by Revzan et al., it is estimated that an incremental 226Ra concentrationof 1 pCi g-’ in soil (from added PG) would result in an increased radon entry rate into a home builton that soil of about 0.7 Bq s-l (19 pCi s-l). For a typical indoor ventilation rate of 1 air change perhour (ach), this would produce an increase in the indoor radon concentration of about 0.3 pCi L-‘.

According to the EPA’s exposure scenarios 5 or 6 (Table l), i.e., previous 100-y biennial PGapplications of about 9,000 lb/acre, the 226Ra concentration in the soil under and around a landreclaimer’s home would be increased by 2.7 pCi g-l, with a consequent increase in the indoor radonconcentration of about 0.9 pCi L-‘. This would approximately double the “background” indoorradon concentration, which is typically about 1 pCi L-’ in Florida. However, the resulting totalradon concentration would still be less than half of EPA’s currently recommended “Action Level”of 4 pCi/L the value at which homeowners are advised to take remedial action to reduce their riskfrom indoor radon exposure (EPA, 1992b).

The EPA chose a much simpler (and less realistic) model to calculate the increment in indoor airconcentration caused by a PG-enhanced 226Ra concentration in the soil beneath a home built onreclaimed agricultural land. Their model considered only the diffusion of radon through assumedcracks in the concrete floor slab, i.e., an assumed “radon diffusion coefficient” for the floor slab.For an unusually high assumed ventilation rate (2 ach), and exposure scenarios 5 or 6, the EPAcalculated an incremental radon concentration in indoor air of 0.3 pCi L-‘. For a more realisticventilation rate (1 ach), this value should be increased to 0.6 pCi L-l, which is then comparable to(but slightly lower than) the value derived from Revzan et al.'s study.

The EPA’s recommended estimates of lifetime risk (of lung cancer) from exposure to radon progenyin a home are 29 in 1,000 (2.9 x 10m2) for cigarette smokers, and 2 in 1,000 (2 x 10-3) for non-smokers, for an average radon gas concentration of 4 pCi L-l (at the Action Level). For the U.S.population as a whole, of which 34% are smokers, the estimate of lifetime lung cancer riskattributable to indoor radon is therefore about 2.8 in 1,000 (2.8 x 10-q per pCi L-’ concentration ofradon indoors. Thus, the estimated additional lifetime risks from indoor radon according to EPA’sexposure scenarios 5 and 6 are:

. 8 in 10,000 according to EPA’s calculation, with 2 ach;

. 16 in 10,000 according to EPA’s calculation, with 1 ach; and,

. 24 in 10,000 according to the Revzan et al. study, with 1 ach.

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Overall lifetime risk

Adding together the estimates of additional lifetime risk resulting from increased direct gammairradiation and indoor radon exposure, the EPA’s and my own estimates of the overall risk (basedon exposure scenarios 5 or 6) are:

. 26 in 10,000 according to EPA’s calculations (with 1 ach); and,

. 24 in 10,000 according to my analysis.

Therefore, this reassessment supports the EPA’s evaluation of the total additional risk to anindividual who lives for 70 years in a home built on reclaimed agricultural land after 100 years ofheavy application of PG. However, the estimated risk depends critically on the assumed applicationrate; if the assumed PG application rate is too high, then the estimated risk is too high pro rata.

Realistic application rate for PG use in agriculture

As Dr. Sumner has reported at this Forum, the maximum rate at which PG is applied to agriculturalland in practice is about 800 lb/acre (for the treatment of subsoil acidity). This would correspondto about 1,600 lb/acre of biennial application, i.e., about one-fifth of the maximum rate assumed bythe EPA in carrying out their assessment of the MIR. Therefore, according to Dr. Sumner’s researchand my analysis of the dose from indoor exposure, the MIR should be reduced to approximately 5in 10,000 (5 x lOA). However, even that value depends on the assumption that the 800 lb/acre/yapplication rate is maintained for 100 years, which appears to be a grossly conservative assumption.In reality, the MIR is likely to be substantially less than 5 x lo”, and in all likelihood less than 3 x10d4, the value deemed by the EPA to be “acceptable” in relation to unrestricted use of PG.

Conclusions from reassessing the MIR for PG use in agriculture

In summary, my conclusions concerning the MIR for use of PG in agriculture are as follows.

l For a given assumed increment of 226Ra concentration in soil, the EPA’s calculationssubstantially overestimate the direct gamma dose received by the occupant of a home built onthat soil, but underestimate by about a factor of two the indoor exposure to radon and itsprogeny.

. The sum of these two components of risk that is obtained from EPA’s calculations is confirmedby the BNWL reassessment, given that EPA’s assumptions about the maximum rate ofapplication of PG to agricultural land are correct.

. The more reasonable assumption of realistic values for the maximum application rate of PG, andfor the likely duration of soil treatment, would reduce the estimated MIR below EPA’s criterionfor “acceptability,” i.e., below 3 x lOA.

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DOSES AND RISKS FROM CONSTRUCTION USES OF PG

To assess the MIR for use of PG in construction, the EPA considered four “maximum reasonableexposure” (MRE) scenarios. The most critical exposures were found to be those received by areclaimer; an individual who builds a house on an old roadbed that incorporated PG in itsconstruction. All four scenarios (numbered 8 through 11) assumed that the road surface had beenlaid on a 0.25-m thick base composed of a 1:2 ratio mixture by mass of PG:soil. Scenarios 8 and9 assumed that the road surface was of asphalt, with the “soil” composed of “clay” or “sand,”respectively. Scenarios 10 and 11 assumed that the road surface was of concrete, whichincorporated PG (15% by mass), again with clay or sand as the soil type.

In the Background Information Document (BID), Section 4.4.2 on page 4-35, the EPA stated that“Reclaimer doses were evaluated for a time (presumed to be 50 years after road construction) whenthe road is closed and the road surface has crumbled and been removed [my italics].” If the PG-containing surface of the concrete road had indeed been removed before building the reclaimer’shouse, then one would expect the exposure conditions to be similar for all four scenarios, i.e., forscenarios 8 and 9 where the road surface was of asphalt, and for scenarios 10 and 11 where the roadsurface was of concrete; only the PG-containing road bed would be left in both cases. However, thedoses and risks calculated by the EPA, as presented in the BID and Final Ruling, were substantiallyhigher in the case of the old concrete road surface than for the old asphalt surface, as follows.

For the home built on a road bed with a net 226Ra concentration of 8.7 pCi g-’ (i.e., one-third the 26-PCi g-l 226Ra concentration in undiluted PG), which had previously been surfaced with asphalt, theFinal Ruling stated that:

. direct gamma dose rate is 71 mrem y-‘, with corresponding lifetime risk of 1.8 x 10-3;

. lifetime risk from indoor radon of 4.3 x lo”, and;. summed lifetime risk is 6.1 x 10-3.

For the home built on the same road bed which had previously been surfaced with concrete, theFinal Ruling stated that:

l direct gamma dose rate is 140 mrem y‘l, with corresponding lifetime risk of 36 in 10,000 (3.6x 10”);

. lifetime risk from indoor radon of 57 in 10,000 (5.7 x lo”), and;

. summed lifetime risk is 93 in 10,000 (9.3 x 10-3).

Clearly, the results presented for the case of the “old concrete” road surface were not calculated asstated in the BID, i.e., on the assumption that the concrete surface had crumbled and been removed.However, according to the EPA’s calculations, even the lower dose and risk cases represented byscenarios 8 and 9 (the old asphalt road surface) yielded an unacceptable estimate of additionallifetime risk. The estimated value of 61 in 10,000 (6.1 x 10-V exceeds the “acceptability” criterionby a factor of twenty.

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Reassessment of Risks to a "Reclaimer” from Use of PG in Road Construction

It would seem reasonable to assume, as was suggested in the BID, that the old road surface, whetherof asphalt or concrete, had been removed before building the reclaimer’s home. It would also seemreasonable to assume that a new concrete floor (of standard 0. l-m thickness) had been laid over theold road bed.

Direct gamma exposure

In this case, the old road bed would contribute a direct gamma exposure (above the “normal”background) amounting to that received from a 0.25-m thick layer of PG-containing soil materialwith a net “%a concentration of 8.7 pCi g-l. Taking account of the shielding provided by the newconcrete floor, the net additional dose rate from the roadbed would then be approximately fifteentimes the value shown earlier for the example of sub-floor soil with a 22?Ra concentration of 0.6 pCig-l. This additional dose rate from direct gamma exposure is therefore estimated to be ~ 15 x 2.4mrem y-‘, i.e., ~ 36 mrem y-‘. Thus:

l the corresponding value of additional lifetime risk from direct gamma exposure isapproximately 9 in 10,000 (9 x lOa).

Indoor radon exposure

Application of the Revzan et al. model to the case of a home with a 0.1-m thick concrete floor builton soil containing 226Ra at a concentration of 8.7 pCi g-’ , the additional concentration of indoorradon is estimated to be approximately 3 pCi L-‘. Thus:

l the corresponding value of additional lifetime risk from indoor radon exposure is approximately80 in 10,000 (8 x 10-3).

Overall lifetime risk

The estimated overall lifetime risk to a reclaimer is about 90 in 10,000; a value close to the EPA’sestimate. This is about thirty times higher than 3 in 10,000 criterion used by the EPA to gauge“acceptability.” Clearly, in this exposure scenario, the additional lifetime risk would be dominatedby the contribution from indoor radon exposure. Even so, it is of interest to note that the estimated3 pCi L“ increase in the indoor radon concentration is still less than the EPA’s currentlyrecommended Action Level (of 4 pCi L-l).

Conclusions from reassessing the MIR for PG use in road construction

Given that the criterion for an acceptable additional lifetime risk is 3 in 10,000, it is clear that areclaimer would be subjected to an unacceptable risk if he or she built a home on a disused road bedthat had been constructed using PG, and lived in the home for 70 years. In order to reduce the

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exposure and resultant risk of premature death to an acceptable level, the ground would first haveto be prepared by excavating the road bed material from under and around the building site. Thiswould add to the cost of the home, but possibly not an unreasonable amount in relation to the totalbuilding cost.

RISKS IN EVERYDAY LIVING

In closing, we can examine the EPA’s criterion for an “acceptable” additional risk to individualswho would choose to live their whole life in a home built on reclaimed agricultural land or an oldroad bed that had been treated with PG in relation to the scale of risks that are part and parcel ofeveryday living. Figure 2. illustrates six examples of such risks. Taking the risk criterion of 3 in10,000 as the reference:

l the risk of dying in an airplane crash is about the same;

l the risk of dying prematurely from cancer caused by the natural radionuclide potassium-40 (“9(>that is present in your own body is two times greater;

. the risk of being killed in a fire in your home is three times greater;

l the risk of being killed by drowning is seven times greater;

l the risk of being killed in a car crash is twenty five times greater, and;

. the risk of being killed in a violent crime is twenty seven times greater.

It should also be borne in mind that these examples of the risks of violent death are each likely toresult in a substantially reduced life-span for the individual concerned. In contrast, any additionalcancer caused by long term exposure to radiation will necessarily occur in old age, and thus havea relatively small effect on the “normal” life-span.

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REFERENCES

Conklin, C., Colli, A., Jonesi, F., Hendricks, D., Gray, L., Bunger, B., and Hung, C.-Y. (1992).Potential Uses of Phosphogypsum and Associated Risks; Background Information Document.EPA 520/1-91-029. U.S. Environmental Protection Agency, Washington, DC.

International Commission on Radiological Protection (ICRP). (1993). Protection AgainstRadon-222 at Home and at Work. ICRP Publication 65. Ann. of ICRP 23(2).

Revzan, K. L., Fisk, W. J., and Sextro, R. G. (1993). Modeling radon entry into Florida slab-on-grade houses. Health Phys. 65(4):375-385.

Rutherford, P. M., Dudas, M. J., and Arocena, J. M. (1995). Radon emanation coefficients forphosphogypsum. Health Phys. 69(4):513-520.

SENES Consultants Ltd. (1992). Review of the phosphogypsum final rule and backgroundinformation document. Report prepared for the Fertilizer Institute, Washington, DC. SENESConsultants Ltd., Richmond Hill, Ontario.

U.S. Environmental Protection Agency. (1992a). National Emission Standards for AirPollutants (NESHAP); National Emission Standards for Radon Emissions from PhosphogypsumStacks, 40 CFR Part 61, Federal Register, Vol. 57, No. 107, June 3, 1992.

U.S. Environmental Protection Agency. (1992b). A Citizen‘s Guide to Radon (Second Edition):The Guide to Protecting Yourself and Your Family From Radon. EPA 402-K92-001. U.S.Environmental Protection Agency, Washington, DC.

U.S. Environmental Protection Agency. (1994). Estimating Radiogenic Cancer Risks. EPA402-R-93-076. U.S. Environmental Protection Agency, Washington, DC.

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